Widespread shifts in the coastal biota of northern California during the 2014–2016 marine heatwaves

During 2014–2016, severe marine heatwaves in the northeast Pacific triggered well-documented disturbances including mass mortalities, harmful algal blooms, and declines in subtidal kelp beds. However, less attention has been directed towards understanding how changes in sea surface temperature (SST) and alongshore currents during this period influenced the geographic distribution of coastal taxa. Here, we examine these effects in northern California, USA, with a focus on the region between Point Reyes and Point Arena. This region represents an important biogeographic transition zone that lies <150 km north of Monterey Bay, California, where numerous southern species have historically reached their northern (poleward) range limits. We report substantial changes in geographic distributions and/or abundances across a diverse suite of 67 southern species, including an unprecedented number of poleward range extensions (37) and striking increases in the recruitment of owl limpets (Lottia gigantea) and volcano barnacles (Tetraclita rubescens). These ecological responses likely arose through the combined effects of extreme SST, periods of anomalous poleward flow, and the unusually long duration of heatwave events. Prolonged marine heatwaves and enhanced poleward dispersal may play an important role in longer-term shifts in the composition of coastal communities in northern California and other biogeographic transition zones.

1. Acanthinucella spirata (Angular Unicorn Snail). The northern range limit for this carnivorous snail has often been published as Tomales Bay (Morris et al. 1980, Hellberg et al. 2001). However, populations of A. spirata have been recorded in Bodega Harbor since at least the 1940s (Colonel Lee O. Miles, unpublished field notes, California Academy of Sciences). Specimens of A. spirata were collected in Bodega Harbor by Col. Miles in 1948-1949LACM 160770). A. spirata was also recorded in Bodega Harbor during the early 1970s (Standing et al. 1975), the mid-1990s (J.T. Carlton, personal communication to ES and JLS), and was still present at this location in 2017 (JLS, personal observation). In 1946, A. spirata was also reported by E.P. Chace at Haven's Neck in Mendocino County, CA (Chace 1948). During June 2017, an intertidal population of A. spirata was discovered by Torre Flagor and Paul Bourdeau, just south of Devil's Gate at Cape Mendocino, CA, representing the new northern range record for this species (Fig. S1;Flagor and Bourdeau 2018). This represents a range extension of 260 km for A. spirata, which is surprising given that this gastropod has benthic egg capsules with crawl-away, juvenile snails. In the absence of planktonic dispersal, it is possible that egg capsules were carried poleward by rafting (Flagor and Bourdeau 2018), or that this population 13. Creseis virgula (Curved Needle Pteropod). The pteropod Creseis virgula is typically a tropical and subtropical species, occurring in warm oceans throughout the world (Bé and Gilmer 1977). In the eastern Pacific, C. virgula ranges from Peru to Southern California (Bé and Gilmer 1977), and can sometimes be abundant in plankton tows south of Point Conception (McGowan 1967). To our knowledge, there is only one record of C. virgula from north of Point Conception, when this species was found at a single offshore station (~37°N, 130°W) during a California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruise in April 1950(McGowan 1967. On 4 November 2014, several C. virgula (including both adults and veliger larvae) were collected by C.V. Davis and E.B. Rivest in a plankton tow at Bodega Line Station 4 (located ~32 km offshore from Bodega Marine Laboratory), a northern range record for this species in the eastern Pacific (Fig. S13).

Dasya binghamiae (Red Alga).
This mid intertidal to subtidal red alga has a published geographic range of Punta Abreojos, Baja California, Mexico, to Bodega Bay in Marin County, CA (Abbott and Hollenberg 1976). The previous northern range record for D. binghamiae was a specimen collected in July 1912 from 0.20 km north of the Estero de San Antonio in Bodega Bay (UC276143). On 18 June 2015, Peter G. Connors collected intertidal D. binghamiae from the South Jetty at the Bodega Harbor entrance (UC2056114), the first record from Sonoma County, CA, and the new northern range limit for this species (Fig. S15).

Delphinus capensis (Long-beaked Common Dolphin).
Delphinus capensis is found in warmtemperate and tropical coastal waters along many of the world's continents (Allen et al. 2011). In the northeast Pacific, the distribution of D. capensis is concentrated along the coast of Mexico, including the Gulf of California, and north to central California (Allen et al. 2011). D. capensis is generally associated with warmer water than its congener, the Short-beaked Common Dolphin (D. delphis). In 1993, several live D. capensis were observed for the first time in British Columbia, Canada (Ford 2005). Other than these isolated northern sightings, this species had not been recorded previously north of Monterey Bay (Ford 2005). For example, in surveys conducted during 1996-2014, D. capensis was not recorded in northern California, Oregon, or Washington (Barlow 2016

Delphinus delphis (Short-beaked Common Dolphin).
Delphinus delphis is found worldwide, primarily in warm-temperate and subtropical waters. In the eastern Pacific, its core geographic distribution extends from Central America northward to Point Conception (Allen et al. 2011). Historically, D. delphis was sighted north of Monterey Bay only occasionally (Allen et al. 2011). During 2014-2016, we observed approximately 25-30 D. delphis offshore at Cordell Bank on three occasions (7 September 2014, 6 September 2015, 18 September 2015; JLS, personal observations; Fig. S17). During October 2015, record numbers of common dolphins were also observed near the Farallon Islands (Point Blue Conservation Science, unpublished data). On 6 January 2017, a dead D. delphis was reported washed ashore at Salmon Creek Beach (iNaturalist 4905297). These observations from northern California were also coincident with reports of an increased abundance of D. delphis at more northerly sites. In particular, the estimated abundance of D. delphis along the coasts of Oregon and Washington during 2014 was twenty times greater than the mean estimate of abundance during 1996-2008 (Barlow 2016). Although a dead D. delphis had been recorded at least once in British Columbia, Canada (Ford 2005), small numbers of live D. delphis were recorded for the first time in British Columbia in late September 2015 (off the southwestern coast of Vancouver Island; Pynn 2015).

Diphyes dispar (Siphonophore).
Diphyes dispar is typically restricted to warmer regions of the Pacific Ocean (Alvariño 1971). Along the Pacific coast of North America, there are numerous coastal records of this species from Baja California, Mexico, and southern California (Alvariño 1971), including near the Channel Islands (e.g., USNM 28508). Diphyes dispar was also collected from Monterey Bay in 1911 (USNM 42119). We are aware of only one prior record of this species from north of Monterey Bay in the northeast Pacific; D. dispar was collected at below 1000m from 42°N, off the coast of Brookings, Oregon (Alvariño 1971). This appears to be the northern range record for this species, although this sampling station was >380 km offshore, and thus was not a coastal occurrence. On 17 September 2014, D. dispar was collected ~100 km offshore from Point Sur, CA (MCZ:IZ:69767). During 2014-2016, JLS and ES recorded D. dispar washed ashore at Salmon Creek Beach on the following 11 dates: 29 August 2014, 14 September 2014 (Fig. S18), 16 September 2014, 27 October 2014, 30 October 2014, 9 February 2015, 17 October 2015, 18 February 2016, 27 February 2016, 6 March 2016 March 2016. On some of these occasions, the distinctive nectophores of this species were common (e.g., >50 nectophores/day encountered).

Doriopsilla albopunctata (White-spotted Sea Goddess Nudibranch).
Doriopsilla albopunctata is a southern species that is rarely recorded north of San Francisco, and is less common than its congener D. fulva in intertidal habitats north of Point Conception (Goddard et al. 2016). We recorded single specimens of D. albopunctata at Bodega Marine Reserve on 15 July 2014 and 16 February 2015 (JLS and ES, personal observations). We recorded a single D. albopunctata at Pinnacle Gulch on 8 July 2016, and three individuals at this site on 13 July 2017. We also recorded three D. albopunctata at Salt Point on 14 July 2017. Doriopsilla albopunctata was previously known to occur as far north as Mendocino County, CA, including Van Damme State Park (Beeman and Williams 1980) and Mendocino, CA . In May 2017, N. Treneman recorded a single specimen of D. albopunctata at Whiskey Creek, Oregon, representing a new northern range record ( Fig. S20; Goddard et al. 2018).

21.
Doriopsilla fulva (White-spotted Dorid Nudibranch). Doriopsilla fulva is typically uncommon north of San Francisco and previously had a northern range limit of Abalone Beach in Humboldt County, CA (Jaeckle 1984). Beginning in February 2015, we observed an increase in abundance of D. fulva in the Bodega Bay region relative to 2004-2014 (JLS andES, personal observations). From 2015-2017, this species was recorded at numerous intertidal sites in central and northern California (iNaturalist records), often in record abundance (Goddard et al. 2016). This nudibranch continued to be common in northern California during 2017, and we recorded 12 individuals at Salt Point on 14 July 2017, and 37 individuals at Salt Point on 13 July 2018 (ES and JLS, personal observations). Doriopsilla fulva was recorded in Oregon for the first time in June 2015, at Whiskey Creek (Goddard et al. 2016). During April-August 2016 and June 2017, Todd Cliff recorded D. fulva farther north, in Netarts Bay, Oregon, its new northern range limit ( Fig. S21; Goddard et al. 2018).

Dosima fascicularis (Blue Buoy Barnacle).
Although this pelagic barnacle has a cosmopolitan distribution (Weisbord 1979), in the north Pacific it is most commonly associated with warmer coastal waters and offshore waters. Dosima fascicularis is common in the diet of offshore Shooty Shearwaters (Puffinus griseus) in the central north Pacific (Shiomi andOgi 1992, Gould et al. 2000), especially at lower latitudes (35-40°N, Shiomi and Ogi 1992). In coastal waters of the northeast Pacific, D. fascicularis is found in the greatest abundance in the warmer waters of southern California (Knudsen 1962). For example, >1,900 D. fascicularis were collected when a 1,000 m stretch of beach in La Jolla, CA, was surveyed on five successive dates (Cheng and Lewin 1976). Dosima fascicularis has occasionally washed ashore in northern California in small numbers, including specimens from Dillon Beach in June 1948 (CASIZ 87489) and Spring 1956 (CASIZ 56379, 87485, 87490), and near Humboldt Bay in June 1936 (CASIZ 21990). Many (but not all) of the coastal records of D. fascicularis from north of California are associated with El Niño events. For example, D. fascicularis was collected from Coos Bay, Oregon, in May 1942, during the strong 1941-1942. Specimens were also collected ~250 km offshore from Tillamook Bay, Oregon (CASIZ 115147), by David L. Stein in July 1973during the strong 1972-1973El Niño. During 1926 fascicularis was collected at Copalis Beach, Washington (CASIZ 15487, 15501, 29157), from north of Vancouver Island, British Columbia, Canada (CASIZ 15473), and at Biorka Island in Southeast Alaska (USNM 78367). These occurrences were associated with the strong 1925-1926 El Niño event. However, there are also a handful of records of D. fascicularis from northern sites that have occurred during ENSO-neutral years. These include collections, for example, from British Columbia (USNM 78368,78369) and Southeast Alaska (UAM 10760, 10761) in 1934 and1994, respectively. The northern record for D. fascicularis appears to be specimens collected in April 1940 from Salisbury Sound, Alaska (UAM 12262). During 2014-2017, we found D. fascicularis washed ashore at Salmon Creek Beach on ten dates: 30 August 2014, 6 September 2014, 21 September 2014, 28 May 2015, 14 June 2015, 5 August 2015, 23 January 2016, 6 March 2016, 20 April 2016, and 27 April 2017JLS and ES, personal observations). The numbers of individuals found were small (generally 2-6 individuals/date, but occasionally as many as 25). On 26 March 2016, S. Morey also found two specimens washed ashore at Arcadia Beach, Oregon ( Fig. S22B; personal communication to ES). During 2014, D. fascicularis was also recorded at several sites in British Columbia. On 11 July 2014, Jackie Hildering, Robin Abernethy, and Jared Towers recorded D. fascicularis about 65 km offshore from the southern end of Moresby Island, British Columbia ( Fig. S22C; J. Hildering, personal communication to ES). On 5 August 2014, J. Hildering found D. fascicularis washed ashore on the southwest shore of Princess Royal Island, British Columbia (J. Hildering, personal communication to ES).

Emerita analoga (Mole Crab).
This suspension-feeding crab is found on intertidal sandy beaches from Baja California, Mexico, to Kodiak Island, Alaska (Jensen 2014). However, E. analoga is most abundant in the southern part of its geographic range between Ensenada, Baja California, Mexico, and central California (Ricketts and Calvin 1968). During previous El Niño events, larvae were sometimes transported northward in abundance leading to high densities of juvenile E. analoga on beaches in Oregon, Washington, and British Columbia, Canada (Ricketts and Calvin 1968, Sorte et al. 2001, Wonham and Hart 2018. The first record of E. analoga in Washington State was coincident with the strong 1941-1942 El Niño event (Banner and McKernan 1943). Similarly, E. analoga was first recorded in British Columbia in June 1959, following the strong 1957-1958 El Niño event (Radovich 1961). During 2016-2017, E. analoga was reported on beaches in Washington (iNaturalist 6014202, 7297400) and British Columbia (iNaturalist 4972976). Wonham and Hart (2018) documented E. analoga (including gravid females) as far north as the west coast of Vancouver Island, British Columbia. Relative to 2004-2013, we observed a massive increase in the density of juvenile E. analoga at Salmon Creek Beach, Pinnacle Gulch, and other local beaches in the Bodega Bay region during 2014-2017 (ES and JLS, personal observations; Fig. S23).

Flabellinopsis iodinea (Spanish Shawl Nudibranch).
Although the northern range limit for this nudibanch is Vancouver Island, British Columbia, Canada (Bernard 1970), this is a southern species that is rarely found north of Monterey Bay (Goddard et al. 2016). We recorded a total of three F. iodinea at Pinnacle Gulch (18 and 19 May 2015; Fig. S24), and Coleman Beach (23 May 2015) (ES and JLS, personal observations). Flabellinopsis iodinea was reported from Trinidad on eight dates between April 2015 and July 2016 (e.g., iNaturalist 3751571, 1387158), and 23 individuals were observed at this location on 4 July 2015 (Goddard et al. 2016). Flabellinopsis iodinea was observed as far north as Cape Flattery, Washington, during August 2015 (Goddard et al. 2018).

Hancockia californica (Hancock's Nudibranch).
Hancockia californica is typically not found north of Dillon Beach, CA, with only a single previous record from Trinidad, CA, reported by Jaeckle (1984). On 23 May 2015, we found one individual at Coleman Beach ( Fig. S25A; JLS and ES, personal observations) and on 7 June 2015, A. Young found one individual at Shell Beach (iNaturalist 1604528). During August 2015, at least three H. californica were recorded at the previously documented northern range limit in Trinidad ( Fig. S25B; Goddard et al. 2016;and iNaturalist 1833410, 1908069, 1908082).

Hespererato vitellina (Appleseed Erato Snail).
Hespererato vitellina is a low intertidal and subtidal snail, with a published northern range limit of Bodega Bay, CA (Morris et al. 1980). 27. Hippopodius hippopus (Siphonophore). The siphonophore Hippopodius hippopus is most commonly found in warmer, tropical waters (Mapstone 2009). It is easily recognized by its distinctive horseshoe-shaped nectophores (Kirkpatrick and Pugh 1984). The northernmost record for H. hippopus in the northeast Pacific was formerly 38°N (Alvariño 1971). However, this record was from far offshore (> 800 km). Coastal records of this species in the northeast Pacific appear to be restricted to locations south of Point Conception (Alvariño 1971). In March 1993, H. hippopus was collected 200 km offshore of Point Conception (Haddock and Case 1999), and this species has been recorded at several locations near the coast of Baja California, Mexico (Alvariño 1971

Hyalocylis striata (Striated Sea Butterfly).
The pteropod Hyalocylis striata is typically a tropical species, occurring in both the tropical and subtropical Pacific and Atlantic Oceans (Tesch 1946, Tesch 1948, McGowan 1967, Bé and Gilmer 1977. California Cooperative Oceanic Fisheries Investigations (CalCOFI) plankton tows conducted along the west coast of North America in November 1949 recorded H. striata at only a single station, off the southern coast of Baja California, Mexico (~24. 2°N;McGowan 1967). Hyalocylis striata has occasionally been recorded in more temperate regions of the central Pacific, e.g., ~2,000 km west of the California coast (35°30'N, 145°00'W; Tesch 1948). We identified three specimens collected along the California coast in late 2014, which to our knowledge are the first records of this pteropod from California. The first specimen (shell length ~4.8 mm) was collected on 24 September 2014 by C.V. Davis, E.B. Rivest, J. Jahncke, and Point Blue Conservation Science in a vertical plankton tow (400m depth to surface) at Bodega Canyon ( Fig. S28A; CASIZ 202355). The second specimen ( Fig. S28B; CASIZ 202356) was a juvenile H. striata (shell length ~0.9 mm) collected on 21 October 2014 by C.A. Vines, D. Dann, and M.G. Susner in a vertical tow (15m depth to surface) at the Bodega Marine Laboratory oceanographic buoy (located 1.2 km offshore from the laboratory). This specimen represents the northern geographic record for this species. Finally, another juvenile H. striata (shell length ~0.33 mm) was collected by C.V. Davis and E.B. Rivest on 4 November 2014 in a plankton tow at Bodega Line Station 4 (located ~32 km offshore from Bodega Marine Laboratory).

Janolus barbarensis (Janolus Nudibanch).
This nudibranch is rare north of Morro Bay, CA, (Goddard et al. 2016), but has been reported previously in San Francisco Bay (Jaeckle 1983). Janolus barbarensis was observed in San Francisco Bay in July-August 2015 (Goddard et al. 2016). It was subsequently recorded in Bodega Harbor on 11 September 2015 by S. Brumbaugh and C.K. Kwan, and on 12 September 2015 by ES and JLS (Fig. S29). These observations in Bodega Harbor represent a new northern range record for J. barbarensis.

Janthina janthina (Violet Sea Snail).
Janthina janthina is a pelagic snail that occurs worldwide in tropical and temperate waters (Beu 2017). In the northeast Pacific, J. janthina is considered "extremely rare" in California (Berry 1958), and is generally only found washed ashore south of Point Conception (Burch 1945). Along the west coast of North America, we are aware of only three prior records of J. janthina north of Point Conception. In October 1960, V.L Yadon collected a single specimen in Pacific Grove (CASIZ 135161). In 1935, June Tapscott collected a single specimen on Salmon Creek Beach (CASIZ 135160). Finally, Florian Von Eschen collected a single specimen of J. janthina (USNM 365148) in Neskowin, Oregon, the northern range record for this species (Fig. S30A). Although no collection date is available, this latter specimen was deposited in the USNM in July 1926 and thus may have been associated with the strong 1925-1926 El Niño event. During spring 2016, JLS and ES observed four specimens of J. janthina washed ashore. Specifically, single specimens were collected on 12 March 2016 and 22 April 2016 on Salmon Creek Beach (Fig. S30B). An additional two specimens were collected on 23 April 2016 in Horseshoe Cove (Bodega Marine Reserve; CASIZ 224106).

Janthina umbilicata (Purple Sea Snail).
Janthina umbilicata is a pelagic snail that is cosmopolitan in warm seas (Beu 2017). J. umbilicata is considered the most common and abundant janthinid species in offshore waters along the coasts of Baja California, Mexico, and California (Savilov 1969). However, it is rarely observed on beaches north of Monterey Bay (Burch 1945). We are aware of five records of J. umbilicata from the Bodega Bay region prior to 2015. In March 1938, a large number of J. umbilicata washed ashore in Bodega Bay (Burch 1945  J. umbilicata on 22 dates and collected >3,000 individuals from Horseshoe Cove, and especially Salmon Creek Beach. This included at least five separate mass stranding events where from 100 to >400 individuals were found washed ashore on a given day (e.g., 22 April 2016, CASIZ 224107).
The prior northern record of J. umbilicata is two specimens collected by Florian Von Eschen in Neskowin, Oregon (USNM 365147). Although no collection date is available, the specimens were deposited in the USNM in July 1926 and thus may have been associated with the strong 1925-1926 El Niño event. A specimen of J. umbilicata (ANSP 320948) collected prior to 1891 is associated with the locality of Icy Cape, Alaska, in the Arctic Pacific. However, several lines of evidence suggest that this specimen is likely mislabeled, and we regard Neskowin, Oregon, as the prior northern range record for this species. There were numerous observations of J. umbilicata at northern sites during 2015-2016.

Jellyella tuberculata (Bryozoan).
Jellyella tuberculata (formerly Membranipora tuberculata) is known "from warm temperate and tropical seas worldwide" (Tilbrook et al. 2001). In the eastern Pacific, it is distributed from Peru to northern California (Soule et al. 2005). Although it has been suggested that its occurrence in central/northern California is linked to El Niño events (Soule et al. 2007), we have found J. tuberculata to be reliably present in the low intertidal zone at Pinnacle Gulch and Dillon Beach since our first search for this species in 2011 (D.S. Swezey and ES, personal observations). This bryozoan appears to reach its northern range limit at Bodega Bay, CA (Swezey et al. 2017). In Fall 2016, there was a striking increase in the abundance of J. tuberculata at Pinnacle Gulch relative to 2011-2014, with colonies blanketing extensive patches of algae in the low intertidal zone ( Fig. S32; ES and JLS, personal observations). J. tuberculata has remained common on algae at this site through our most recent survey in November 2018.

Lepidochelys olivacea (Olive Ridley Sea Turtle).
Lepidochelys olivacea is found worldwide, primarily in tropical and subtropical waters (NMFS and USFWS, 1998b). In the eastern Pacific, L. olivacea occurs most commonly from Peru to southern California, but this species is observed occasionally stranded on beaches in northern California, Oregon, and Washington, and has been recorded previously as far north as Alaska (Hodge and Wing 2000). On 15 January 2016, we observed a fresh carcass of L. olivacea washed ashore at Salmon Creek Beach ( Fig. S33; JLS and ES, personal observations). This observation during winter 2015-2016 was coincident with at least nine strandings of L. olivacea in Oregon and Washington, an unprecedented number of northern records for a single year (Valdes 2016).

Lissothuria nutriens (Scarlet Sea Cucumber).
The northern range limit of this low intertidal to subtidal sea cucumber has long been recognized as Bodega Head (Wootten 1949), although it has been rare at this site historically (Rutherford 1975

Lottia gigantea (Owl Limpet).
Lottia gigantea is a territorial, mid to high intertidal limpet that ranges from Baja California, Mexico, to Point Cabrillo in northern California (Fenberg and Rivadeneira 2011). Lottia gigantea reaches its highest density in southern California and has historically occurred in low abundance north of Monterey Bay (Fenberg and Rivadeneira 2011  We are not aware of museum samples from the Bodega Bay region collected after 1951. In 1964, there was a small population of large L. gigantea at Duxbury Reef that dwindled to a few remaining individuals by the early to mid-1970s (Armand Kuris, personal communication to ES). Otherwise, L. gigantea appears to have been scarce or absent in this region during the 1960s and 1970s. In particular, L. gigantea was not observed in the Bodega Marine Reserve (BMR) during the 1970s (Ristau et al. 1978; J.T. Carlton and A. Kuris, personal communication to ES). When we first began working in BMR in 2005, a small population of L. gigantea was present (JLS and ES, personal observations). Our 2010 survey at this site documented only larger individuals with no evidence of recent recruitment ( Figure 4). During 2011-2014, we noted the loss of some larger L. gigantea from the BMR population, but never recorded the presence of small individuals (JLS and ES, unpublished data). This observation is consistent with surveys conducted at other sites in this region during 2004-2006, which also revealed little evidence of recent recruitment in northern California. In particular, no juveniles (<25 mm length) were found at Dillon Beach, CA, or six sites north of that location (Fenberg and Rivadeneira 2011). As indicated by our survey data ( Figure 4), large numbers of L. gigantea recruited to BMR during winter 2014-2015 and winter 2015-2016 (Fig. S35). We also documented a high percentage of juvenile limpets in other nearby populations during 2016-2017 (JLS and ES, unpublished data), indicating widespread recruitment of L. gigantea in this region in association with warm water conditions during 2014-2016. Historically, the northern range limit for L. gigantea was Crescent City, CA, based on museum specimens collected in four different years: 1889, 1935, 1957, and 1963(Fenberg and Rivadeneira 2011. However, Fenberg and Rivadeneira (2011) did not find L. gigantea present at Crescent City during surveys conducted in 2003, 2005, and 2011. Similarly, we were unable to locate any L. gigantea at Crescent City during extensive searches in May 2017 (JLS and ES, personal observations). Thus, despite increases in the abundance of L. gigantea in northern California during 2014-2017, it appears that the current northern range limit for this species remains in Mendocino County, CA (Fenberg and Rivadeneira 2011;JLS and ES, unpublished data). Note that the northern range limit for L. gigantea has been listed as Neah Bay, Washington, in some publications (McLean 1966, Morris et al. 1980). This record stems from observations by Robert Talmadge, who reported finding two L. gigantea in Neah Bay, presumably in the late 1950s or early 1960s (R. Talmadge, personal communication to J.T. Carlton). Although there are no known specimens or photographs associated with this rare northern occurrence, R. Talmadge was an accomplished naturalist and malacologist, so the identification and record are likely valid (J.T. Carlton, personal communication to ES).

Megabalanus californicus (Pink-striped Barnacle).
Megabalanus californicus is a southern barnacle, usually regarded as "very uncommon north of Monterey" (Newman and Abbott 1980). Its published northern range limit is Humboldt Bay (Zullo 1968), based on specimens collected from buoys in this location in 1939 (CASIZ 24476). Megabalanus californicus was reported at Cordell Bank during 1980and 1981(Newman and McConnaughey 1987. In 1996, two M. californicus shells were observed washed ashore in Horseshoe Cove ( During 2015-2017, there was a noticeable increase in the local abundance of M. californicus in Bodega Bay. During this period, live M. californicus was observed growing on low intertidal mussel shells, kelp holdfasts, and a crab carapace (Pugettia producta) in Bodega Marine Reserve, and M. californicus shells and plates were routinely found washed ashore (JLS and ES, personal observations). In March 2016, we recorded >500 M. californicus growing on the Bodega Marine Laboratory oceanographic buoy (JLS and ES, personal observations). On 11 December 2014, the St. Georges oceanographic buoy (NOAA Buoy 46027, located 14.8 km northwest of Crescent City, CA) was dislodged from its mooring. This buoy washed ashore three days later in Cape Sebastian, Oregon, where Nancy Treneman photographed at least nine M. californicus growing on mussels attached to the buoy. On 5 June 2015, a single M. californicus was photographed by N. Treneman in the low rocky intertidal zone at Humbug State Park, Oregon (Fig. S36), representing the current northern range record for this species. In addition, during July-September 2015, several clusters of M. californicus were collected by N. Treneman and David Bilderback from bull kelp holdfasts that had washed ashore in Bandon, Oregon, suggesting that this species might have settled north of Humbug State Park (although it is not possible to identify where the bull kelp originated). During El Niño periods, M. californicus has been observed on the hulls of ships moored in British Columbia, Canada, including specimens collected in 1925 (CASIZ 094120; and RBCM A-269-00001) and 1958 (RBCM 979-11147-256). However, there is no definitive evidence of this species occurring on benthic substrate in British Columbia (but see Cornwall 1955, Carlton et al. 2011.

Mola mola (Ocean Sunfish).
Mola mola is a large, pelagic fish that occurs globally in tropical and temperate waters. In some regions, M. mola undergoes seasonal migrations to track warmer water (Sims et al. 2009). In the eastern Pacific, M. mola ranges from Chile to the Gulf of Alaska (Love et al. 2005). Unusual past occurrences of M. mola in the coastal waters of Washington, British Columbia, Canada, and Alaska have been associated with warm water temperatures during strong El Niño events, including those in 1925-1926, 1982(Hubbs 1948, Pearcy and Schoener 1987, Mecklenburg et al. 2002, Brodeur et al. 2006. During 2014-2015, we noted an increase in abundance of M. mola during offshore pelagic trips to Bodega Canyon/Cordell Bank (

Navanax inermis (California Aglaja).
Navanax inermis is a southern heterobranch gastropod (Family Aglajidae) that is found on soft and hard substrata, where it preys on other heterobranchs, particularly bubble snails and soft-bodied nudibranchs. Navanax inermis is most common in southern California, but has been observed occasionally in Elkhorn Slough (Ricketts and Calvin 1968). Navanax inermis was also reported previously from Bolinas Lagoon and Bodega Bay in association with El Niño events (Goddard et al. 2016). In particular, Standing et al. (1975) reported that N. inermis was rare to common in Bodega Harbor during a sampling period that included the strong 1972-1973 El Niño event. On 4 June 2015, N. inermis was observed by Grace Ha in Bodega Harbor, its northern range limit (JLS and ES, personal observation). Navanax inermis was recorded again in Bodega Harbor during June, July, and August 2016 by JLS, M. Whalen, and Grace Ha, respectively (Fig. S38). During 2015-2016, this species was also noted in Drakes Estero (iNaturalist 3871263) and Tomales Bay (iNaturalist 2354769, 2358770, 4594938).

Oceanodroma melania (Black Storm-Petrel). Oceanodroma melania nests on islands in
Baja California, Mexico, and southern California and then disperses northward after the breeding season, primarily to southern and central California (Ainley 2008). Although O. melania regularly occurs in Monterey Bay, only small numbers have historically been seen farther north, including Cordell Bank (Howell 2012). However, O. melania has become more abundant in offshore waters north of Monterey Bay since 2007 (Ainley 2008, eBird 2017, a trend seen in some other primarily southern seabirds such as Sula leucogaster (Davis et al. 2017). The abundance of O. melania off the California coast is also considered a strong indicator of warm-water anomalies, with large population increases observed during previous El Niño events (Ainley 1976, Hyrenbach and Veit 2003, Spear and Ainley 2007.

Oceanodroma tethys (Wedge-rumped Storm-Petrel). This seabird breeds on the Galapagos
Islands and along the coast of Peru. Densities of Oceanodroma tethys are positively correlated with water temperature (Spear and Ainley 2007). This species' geographic distribution at sea extends northward to offshore of the coast of Baja California, Mexico, although it is considered uncommon to rare in this region (Howell 2012

Okenia angelensis (Los Angeles Okenia Nudibranch).
Okenia angelensis is a southern species that had been recorded as far north as San Francisco Bay on only a single occasion in September 1964 (Lance 1966

Okenia rosacea (Hopkins' Rose Nudibranch).
Okenia rosacea is rarely seen north of San Francisco, but was reported as far north as Cape Arago, Oregon, during the strong 1997-1998 El Niño (Goddard et al. 2016;iNaturalist 2982117). We first observed O. rosacea (14 individuals

Ophichthus triserialis (Pacific Snake Eel).
Ophichthus triserialis is primarily a subtropical eel with a published geographic range from Peru to northern California (Love et al. 2015). It is considered rare north of Baja California, Mexico (Eschmeyer and Herald 1983), and we are aware of relatively few historical records of O. triserialis from north of Point Conception. Three specimens were collected in San Francisco Bay in 1931, 1933. From north of San Francisco Bay, a specimen was collected from Tomales Bay in 1916 or before (Hubbs 1916). In September 1977, a specimen was caught off Bodega Bay (CAS-ICH 40255). The prior northern record for O. triserialis was a 90 cm individual caught offshore of the Klamath River in October 1972 during a strong El Niño event (Quirollo and Dinnel 1975 (Pickens et al. 2018). Lea and Rosenblatt (2000) suggested that larval Ophichthus might be transported north from Baja California with anomalous northward currents associated with El Niño events. The occurrence of large O. triserialis (89-101 cm length) at northern locations during 2014 and 2017 suggests that adult Ophichthus may also migrate northward during warm-water events.

Ophiothrix spiculata (Glass-spined Brittle Star)
. This brittle star formerly had a published northern range limit of San Mateo County, CA (Morris et al. 1980

Pachythyone rubra (Red Sea Cucumber).
This low intertidal to subtidal sea cucumber is usually considered a narrowly distributed endemic species with a published geographic range of Los Angeles to Monterey Bay (Morris et al. 1980, Bergen 1996, Ekert 2007, Lambert 2007. However, records from museum collections suggest a somewhat broader geographic distribution. A subtidal specimen of P. rubra was dredged from Bahia de Ballenas, Baja California, Mexico, in May 1888 (USNM E 2354), and another subtidal specimen was collected just north of Isla Todos Santos, Baja California, Mexico, in April 1998 (Carpizo-Ituarte and Ramos Rivera 2017). At the northern end of its range, a brooding individual was collected from the intertidal zone at Pinnacle Gulch by James Rutherford in July 1976 (Bodega Marine Laboratory synoptic collection). Pachythyone rubra was also recorded in intertidal surveys at Año Nuevo Cove during 1971-1973, and at Año Nuevo Cove and Pigeon Point during 1996(Zabin et al. 2013). On 30 December 2017, ES collected a single P. rubra from the low intertidal zone at Bodega Marine Reserve, representing the new northern record for this species (Fig. S45; CASIZ 227281). Species identification was confirmed by ES by examination of skin and tube foot ossicles (Bergen 1996).

Panulirus interruptus (Spiny Lobster).
Panulirus interruptus lives in subtidal rocky reef habitats and is rarely found north of Point Conception (Ricketts and Calvin 1968). Researchers with extensive diving experience in Monterey Bay report never having seen P. interruptus in that region (Steve I. Lonhart and James M. Watanabe, personal communication to ES). One juvenile P. interruptus (carapace length = 44 mm) was collected from Monterey Bay, sometime prior to December 1895 (USNM 19078), based on the USNM catalog number (Martha Nizinski, personal communication to ES). Although the northern range limit for this species is often reported as Monterey Bay (Duffy 1973), an adult P. interruptus (carapace length = 120 mm) was collected from San Francisco Bay in March 1940 ( Fig. S46A; USNM 104212). More recently, in April 2015, a small juvenile P. interruptus was collected from Monterey Bay (CASIZ 220945). In August 2016, a juvenile P. interruptus was collected in Oyster Point Marina, San Francisco Bay (CASIZ 219743). Seventeen P. interruptus were also reported from Crissy Field in San Francisco between September 2013 and September 2017 based on molts and/or remains of dead lobsters (iNaturalist records). R.F. Johnson collected three spiny lobsters washed ashore at Duxbury Reef in September 2011 (CASIZ 193049) Fig. S46B; CASIZ 224109), which represents a new northern range limit for the benthic lobster phase. Although the carapace was missing, based on the rest of the intact exoskeleton, we estimated the carapace length (CL) of this specimen to be ~55-60 mm. Juvenile P. interruptus are estimated to reach a CL of 55-60 mm in nature in three years (Serfling and Ford 1975), so the size of this lobster suggests that it likely settled in 2014.

Paraconcavus pacificus (Red-striped Barnacle).
Paraconcavus pacificus is a low intertidal to subtidal barnacle often found growing on sand dollars (Dendraster excentricus). Although the northern range limit has been reported as Monterey Bay (Newman and Abbott 1980), this barnacle has long occurred as far north as Ocean Beach in San Francisco, CA, with multiple museum specimens collected from this location between 1912 and 1994 (e.g., CASIZ 93558, CASIZ 98210, CASIZ 98208; see also Mooi 1997). Merrill and Hobson (1970)  48. Petaloconchus montereyensis (Monterey Tube Snail). The northern range limit of this vermetid gastropod is often published as Monterey Bay (Morris et al. 1980). However, this species was recorded as far north as Bodega Bay over 150 years ago (Stearns 1867, as Bivonia compacta). The earliest museum record of P. montereyensis from the Bodega Bay region appears to be specimens collected in June 1941 at Tomales Point by Olga Hartman (CASIZ 227847). We have noted P. montereyensis shells (presumably from subtidal populations) commonly washed ashore at Horseshoe Cove (Bodega Marine Reserve) since we first began working at this site in 2004 (ES and JLS, personal observations), and field notes suggest that these shells have been common at this location since at least the 1970s (J.T. Carlton, unpublished notes from July 1972). In November 2007, we recorded P. montereyensis in the intertidal zone as far north as Van Damme State Park, but we have been unable to locate this species at sites farther north in California or Oregon (ES and JLS, personal observations). A morphologically similar vermetid (P. compactus) occurs in the San Juan Islands, Washington, and Vancouver Island, Canada (Kozloff 1987). This species has sometimes been considered synonymous with P. montereyensis (Hadfield 1989). It is presently unknown whether there are in fact two species of Petaloconchus along the west coast of North America, or whether these are populations of a single species (P. compactus) with a disjunct geographic distribution (Rüdiger Bieler, personal communication to ES). During 2014-2017, P. montereyensis underwent a striking increase in abundance in the intertidal zone at Bodega Marine Reserve. During 2004-2014, we could reliably find small clusters of these tube snails in the Bodega Marine Reserve on only two isolated rock walls in the low intertidal zone. In contrast, by winter 2017, this gastropod was widespread and locally abundant in the low intertidal zone across a large area of Bodega Marine Reserve (ES and JLS, personal observations). During this same period, we observed a similarly striking increase in the intertidal abundance of P. montereyensis at Salt Point State Park (Fig. S48; ES and JLS, personal observations).

Petrolisthes manimaculis (Chocolate Porcelain Crab).
Prior to 1999, the northern range limit for P. manimaculis was recognized as Bodega Bay (Jensen 1995, Morris et al. 1980. Petrolisthes manimaculis was not observed in the Bodega Marine Reserve during the 1970s (Ristau et al. 1978). Petrolisthes manimaculis was, however, collected from the North Jetty

Phidiana hiltoni (Hilton's Nudibranch).
The range expansion of Phidiana hiltoni has been well documented. This species had a northern range limit of Monterey Bay prior to 1977, but by 1992 had expanded north to Duxbury Reef, CA (Goddard et al. 2011). Goddard et al. (2011Goddard et al. ( , 2016 hypothesized that Point Reyes might be a significant barrier to further expansion of P. hiltoni, given its crawling, lectithotrophic larval form and the extensive sandy beaches of Point Reyes National Seashore.

Physophora hydrostatica (Hula Skirt Siphonophore).
Although this siphonophore has a global distribution (Alvariño 1971), most records of this species in the northeast Pacific occur at lower latitudes. For example, P. hydrostatica has been recorded off the coast of Baja California, Mexico (Alvariño 1967), and in the Gulf of California (YPM IZ 035820). The previous northern range limit for this species along the California coast was Monterey Bay, with records from 1968 (CASIZ 95481), 2006 (Gasca et al. 2015),

Pleuroncodes planipes (Pelagic Red Crab).
This pelagic crab is generally restricted to waters off central and southern Baja California, Mexico (Boyd 1967). Pleuroncodes planipes has been observed in California rarely, but large numbers washed ashore in Monterey Bay in association with strong El Niño events in 1859, 1960 (Glynn 1961, Boyd 1967), 1973(CASIZ 003694), and 1982(Wells et al. 1990. Pleuroncodes planipes was also observed offshore of Monterey Bay during the 1997-98 El Niño (Marinovic et al. 2002). In 1983, P. planipes was observed as far north as the Farallon Islands (Ainley 1990). The only known historical records of this species north of San Francisco, CA, are from 1985. In this year, three individuals were collected at Duxbury Reef, CA (CASIZ 173779) and P. planipes was also reported as far north as Fort Bragg (Pearcy et al. 1985).

Polycera atra (Orange-spike Polycera Nudibranch).
This southern nudibranch is generally restricted to protected bays and harbors and is typically found only as far north as Point Reyes, CA (Morris et al. 1980). In association with the strong El Niño events of 1982-1983 and 1997-1998, P. atra was recorded as far north as Oregon and Washington (Goddard et al. 2016). JLS and ES recorded a high abundance of P. atra on the floating docks in Spud Point Marina, Bodega Harbor, during October 2014 and September 2015 (Fig. S53). In May 2016, P. atra was recorded in the harbor at Crescent City by Alison Young (iNaturalist 3219430). Polycera atra was also found in the Charleston boat basin, Oregon, in June 2015 (Goddard et al. 2016), and during July-August 2015, was found on Vancouver Island, British Columbia, representing a new northern range record (Goddard et al. 2018).

Polycera hedgpethi (Hedgpeth's Nudibranch).
This southern nudibranch was first described from specimens collected in Tomales Bay, CA (Marcus 1964). Although its geographic distribution has been described as ranging from Baja California, Mexico, to Tomales Bay (Beeman and Williams 1980), P. hedgpethi was reported as far north as Bodega Harbor during a sampling period that included the strong 1972-1973 El Niño event (Standing et al. 1975). We did not observe P. hedgpethi in Bodega Harbor during 2004-2014 (JLS andES, personal observations). In November 2015, K. Norris and M.A Whalen observed P. hedgpethi in Bodega Harbor (personal communication to JLS), and we subsequently photographed several P. hedgpethi at this site during November 2015 ( Figure S54).

Portunus xantusii (Xantus' Swimming Crab).
This low intertidal to subtidal crab is found on sand flats and in eelgrass beds. Its northern range limit was formerly reported as Santa Barbara, CA (Morris et al. 1980), but in 1999 it was found as far north as Morro Bay, CA, following the 1997-1998 El Niño event (Jensen 2014

Pseudoceros luteus (White Flatworm).
Pseudoceros luteus is a primarily southern flatworm that formerly had a published northern range limit of Monterey Bay (Morris et al. 1980). In  August-November 2015 (iNaturalist 1892041, 1956261, 2180423, 2358716), and in Tomales Bay in August 2015 (iNaturalist 1852549) and September 2016 (iNaturalist 4153031). We are aware of only one record of this flatworm north of Bodega Harbor. Lamb and Hanby (2005) reported a single P. luteus was collected by Doug Swanston near Tofino, British Columbia, Canada. This specimen was photographed in early May 1997 (B. Hanby, personal communication to ES), and thus its appearance in British Columbia was coincident with the strong 1997-1998 El Niño event. Although Tofino, British Columbia, is the northern range record for P. luteus, we are aware of no occurrences of this species in British Columbia since 1997 (D. Swanston, A. Lamb, and B. Hanby, personal communication to ES), nor has it been reported from any locations north of Bodega Harbor.

Puffinus opisthomelas (Black-vented Shearwater).
Puffinus opisthomelas is common along the Pacific coast from Baja California, Mexico, to as far north as Point Conception in southern California. In years of warm ocean temperatures, thousands of P. opisthomelas disperse farther north to Monterey Bay (Keitt et al. 2000, Howell 2012). In these years, small numbers of individuals have also been observed north of Monterey Bay, on rare occasions reaching as far north as Vancouver Island, British Columbia, Canada (Keitt et al. 2000, Howell 2012). The abundance of P. opisthomelas in central California is considered a strong indicator of warmwater anomalies, with large population increases observed during previous El Niño events (Ainley et al. 1995, Hyrenbach andVeit 2003).

Pyrosoma atlanticum (Pyrosome).
This pyrosome (pelagic tunicate) has a global distribution in tropical and temperate oceans (Wrobel and Mills 1998). In the northeast Pacific, P. atlanticum was frequently documented in surveys conducted off the coast of southern California during 1951(Lavaniegos and Ohman 2003. Similarly, surveys conducted off the central California coast during 1983-2002 often recorded P. atlanticum in low abundance (Wells et al. 2013). At higher latitudes, P. atlanticum has been observed only rarely in surveys conducted >80 km off Newport, Oregon, prior to 2016 (Jennifer Fisher, personal communication to ES). Although the geographic range limit of P. atlanticum in the northeastern Pacific has not been defined well, this species was observed previously at least as far north as Puget Sound, Washington, in 2003 (USNM 14572). We recorded P. atlanticum washed ashore at Salmon Creek Beach on at least 14 dates between December 2014 and February 2017 (Fig. S58), but did not record this species during 2004-2013 (JLS andES, personal observations). Pyrosoma atlanticum was abundant on some of these dates (i.e., hundreds of colonies washed ashore on 1 km of Salmon Creek Beach). Similarly, P. atlanticum was observed in record abundances off the coast of central California in 2015 (Sakuma et al. 2016), and off the coasts of Oregon and Vancouver Island, British Columbia, Canada, in Summer 2017 (Sutherland et al. 2018. Pyrosoma atlanticum was also recorded washed ashore along the Oregon coast in December 2016 (iNaturalist 4862742) and 2017 (e.g., iNaturalist 5227221), and as far north as southeast Alaska during January-April 2017 (e.g., iNaturalist 5007884, 5118649). In general, there does not seem to be an association between periodic increases in the abundance of P. atlanticum in southern California and past El Niño events during 1951(Lavaniegos and Ohman 2003. In addition, there was a relatively large increase in the abundance of P. atlanticum in central and southern California in 2012 that was apparently unrelated to a warm-water event (Wells et al. 2013). Thus, although it remains unclear whether P. atlanticum populations in central and southern California are influenced by El Niño events, the recent appearance of large numbers of P. atlanticum at more northerly locations was highly anomalous and coincident with the marine heatwaves (Sutherland et al. 2018).

Sula leucogaster (Brown Booby).
Sula leucogaster breeds on tropical and subtropical islands throughout the world, and historically was rarely observed in California (Ainley 1976). However, S. leucogaster has been recorded annually in California since 1990, with rare sightings off the coasts of Oregon and Washington (California Bird Records Committee 2007), and a single unconfirmed record from the Bering Sea, Alaska, in July 2000 (Tobish 2016). In California north of San Francisco, there were <10 records of S. leucogaster between 1998(California Bird Records Committee 2007, Tietz and McCaskie 2018, and there were only two records from Sonoma County, CA, both in 2013 (eBird 2017). In association with warm-water conditions during 2014-2015, there was a striking increase in S. leucogaster sightings in northern California, with >75 reports north of San Francisco extending to Del Norte County, CA (Rogers et al. 2015, Davis et al. 2017. In October 2015, as many as 30 individuals were observed at the Farallon Islands (Davis et al. 2017). During 2014-2015, there were five records of S. leucogaster in Sonoma County (eBird 2017). During 2014-2015, there was also an increased frequency of S. leucogaster records off the Pacific Northwest, with up to seven records from Oregon and at least eight records from Washington (Irons et al. 2016, Waggoner andMerrill 2017), and five records from British Columbia, Canada (Charlesworth 2016, Charlesworth 2017. Finally, four S. leucogaster were observed in Alaska in 2014 and 2015, with three records from coastal Southeast Alaska, and one individual observed off Amlia Island in the Aleutian Islands in August 2015 (Tobish 2016, Tobish 2017. Northern observations of S. leucogaster continued into 2016-2017, including a sighting of S. leucogaster in Tomales Bay ( Fig. S59; 6 February 2016).

Synthliboramphus hypoleucus (Guadalupe Murrelet).
Synthliboramphus hypoleucus nests on offshore islands along the Pacific coast of Baja California, Mexico. Following the breeding season, very small numbers of S. hypoleucus disperse to areas well offshore of central California in most years (Chesser et al. 2012). Records of S. hypoleucus north of central California are rare and are often associated with warm-water years (Ainley 1976, Ainley et al. 1995. S. hypoleucus appears to seek warmer water during the non-breeding season and will disperse as far north as temperatures allow (Ainley 1976), occasionally reaching waters off the coast of Washington (Chesser et al. 2012

Tetraclita rubescens (Pink Volcano Barnacle).
Prior to the 1980s, this intertidal barnacle was regarded as rare north of San Francisco, with single specimens collected at Shell Beach, CA, in 1957 and1970, and two specimens collected at Fort Ross State Park, CA, no later than the early to mid-1970s (Dawson et al. 2010). In 1984, T. rubescens was found at Sea Ranch and Saunders Reef, CA, by J.S. Pearse (Dawson et al. 2010), and in 1995-1996 a single individual was recorded at Cape Mendocino, CA (Connolly & Roughgarden 1998). In 2007, the northern range limit of T. rubescens was established when a single individual was found by the Coastal Biodiversity Survey (P.T. Raimondi, UC Santa Cruz) at Burnt Hill, Oregon, although the individual was no longer present in a subsequent survey (Dawson et al. 2010).

Thalia democratica (Salp).
Thalia democratica is a salp (pelagic tunicate) found globally in tropical and warm temperate waters (Wrobel and Mills 1998). In the northeast Pacific, Berner (1957) reported that T. democratica was most common in waters with a mean temperature of 14-21°C. Similarly, in the Mediterranean, T. democratica was associated with water temperatures >15.5°C (Licandro et al. 2006). Warmer temperatures approaching 20°C appear to shorten the generation time of T. democratica and can lead to rapid population blooms (Licandro et al. 2006). Thalia democratica can be very abundant offshore along the coasts Baja California, Mexico, and southern California (Berner 1957, Blackburn 1979. In association with the 1963-1964 El Niño event, small numbers of T. democratica were observed as far north as Newport, Oregon, the northern range limit for this species in the northeast Pacific (Hubbard andPearcy 1971, Lavaniegos andOhman 2003). We recorded T. democratica washed ashore at Horseshoe Cove on 25 August 2014 and 14 September 2014 (Fig. S62) and on Salmon Creek Beach on 17 October 2015, but we did not observe this species during 2004-2013 (JLS and ES, personal observations). Our observation from 25 August 2014 was a mass stranding event of thousands of zooids.

Thetys vagina (Salp).
This large salp (pelagic tunicate) is broadly distributed in warmer waters of the Atlantic, Pacific, and Indian Oceans (McAlice 1986, Wrobel andMills 1998). In California, interannual variation in the abundance of T. vagina does not appear to be strongly correlated with El Niños or other warm-water events (Wells et al. 2013, Sakuma et al. 2016. However, records of T. vagina at sites north of California are uncommon and appear to be associated with El Niño events. For example, T. vagina was observed off the coast of Oregon in association with the El Niño events of 1963-1964(Hubbard and Pearcy 1971), 1982(Pearcy et al. 1985. Prior to 2014, the northern range record for Thetys in the northeast Pacific appears to be a specimen collected at Grays Canyon (

Thylacodes squamigerus (Scaled Tube Snail).
This vermetid gastropod occurs in the low intertidal zone of rocky shores and has a published northern range limit of Monterey Bay (Morris et al. 1980). Thylacodes squamigerus was collected from Pacific Grove as early as 1910 (CASIZ 119499), but was apparently uncommon in the Monterey Bay region until sometime after 1973. Thylacodes squamigerus was absent from transect surveys conducted at Hopkins Marine Station (Pacific Grove) in 1931-1933(Sagarin et al. 1999. Similarly, T. squamigerus was absent from surveys conducted at 10 sites in northern Monterey Bay during 1971-1973(Sagarin et al. 1999, Zabin et al. 2013, and Ricketts and Calvin (1968) reported this species as "only occasional in the Monterey Bay region." In contrast, T. squamigerus was common at many sites in Monterey Bay by the mid-1990s (Sagarin et al. 1999, Zabin et al. 2013. This species was also found as far north as Half Moon Bay in 1994 (Sagarin et al. 1999 (Fig. S64), a new northern range record for this species.

Triopha maculata (Spotted Triopha Nudibranch).
Triopha maculata is a primarily southern nudibranch that can be very common in Monterey Bay tidepools (Nybakken 1978). Its northern range limit was reported previously as Bodega Bay (Ferreira 1977), although MacFarland (1966) reported that T. maculata ranged as far north as Crescent City, and Jaeckle (1981) reported this species at Patrick's Point State Park. Millen (1983) reported a new northern range record for T. maculata at Bamfield, Vancouver Island, British Columbia, Canada, presumably in association with the 1982-1983 El Niño event. During September and October 2015, 19 specimens of T. maculata were observed by Jackie Hildering in the shallow subtidal zone at Bear Cove, Port Hardy, Vancouver Island, British Columbia (Fig. S65), a new northern range record for this species (Goddard et al. 2018).

Tursiops truncatus (Common Bottlenose Dolphin).
Tursiops truncatus occurs worldwide in tropical, subtropical, and warm-temperate waters (Allen et al. 2011). In the northeast Pacific, a relatively small population of T. truncatus (~450 dolphins) inhabits coastal waters, whereas a distinct, larger population of ~3,500 occurs offshore (Halpin et al. 2018). The coastal population of T. truncatus was historically known primarily from south of Point Conception (Allen et al. 2011). However, some T. truncatus extended their coastal range north to Monterey Bay during the 1982-1983 El Niño event (Wells et al. 1990). Some T. truncatus remained in central California and subsequently moved north to San Francisco Bay, where they have been regularly observed and monitored since 2010 (Bill Keener, Golden Gate Cetacean Research, personal communication to JLS). One of the first sightings of coastal T. truncatus north of San Francisco was off Doran Beach in July 2012 (Darris Nelson, personal communication to JLS). Since September 2014, coastal observations of T. truncatus north of San Francisco have become more common. From 2015-2017, T. truncatus were reported at sites between Dillon Beach and the Russian River (Fig. S66) on a frequent basis (>25 times; JLS and ES, personal observations; and reports to JLS). During this period, the farthest north coastal observation of T. truncatus was from Little River, CA, in April 2016 (Bill Keener, personal communication to JLS), a new northern range record for the coastal ecotype. The offshore population had been observed previously as far north as 41°N. However, in July 2017, T. truncatus was observed 180 km off the coast of British Columbia, Canada (Halpin et al. 2018). This is the first confirmed record of T. truncatus in Canadian waters and represents a new geographic range record for this species in the northeast Pacific (Halpin et al. 2018). However, because our study is focused on the distribution of coastal biota, we focus here on the range extension of the coastal ecotype of T. truncatus (Table 1).

Velella velella (By-the-wind Sailor).
Velella velella is a pelagic, colonial hydrozoan that occurs globally in warm to warm-temperate waters (Wrobel and Mills 1998). Although small numbers are washed ashore on beaches in northern California during most years, mass strandings on northern beaches are often associated with strong El Niño events. For example, during the major 1925-1926 El Niño, V. velella were abundant as far north as British Columbia, Canada (Hubbs 1948). Similarly, during the strong 1957-1958 El Niño, an increased abundance of V. velella was noted from San Francisco to Alaska (Radovich 1961). Widespread sightings of V. velella also occurred in British Columbia during the 1982El Niño (Pearcy and Schoener 1987. Hubbs (1948) hypothesized that mass strandings of V. velella during El Niño events likely arise from onshore transport of animals from warmer, offshore waters. During 2014 and 2015, we observed mass strandings of V. velella on Salmon Creek Beach on multiple dates ( Fig. S67; JLS and ES, personal observations). Velella velella were also observed during this period in large numbers along much of the U.S. Pacific coast as far north as Sitka, Alaska (e.g., iNaturalist 5102488, 9196515).

B. ACKNOWLEDGEMENTS:
For their contributions to our investigations of recent and historical observations of coastal biota, we are especially grateful to James T. Carlton, Christina Piotrowski, Molly Engelbrecht, Jackie Hildering, Mike Kelly, and Steve Morey.
We thank the following museums, databases, curators, and staff scientists for access to their collections, records, and data:     (Goddard et al. 2016(Goddard et al. , 2018. We compiled dates of observation for species whose egg-laying has been recorded by multiple sources including MacFarland (1966), Costello (1938), Goddard (1984), Goddard (unpublished data, 1975Goddard (unpublished data, -2018, and images on iNaturalist (www.inaturalist.org). We used observations from Rancho Palos Verdes, California (near the southern edge of the Oregonian Biogeographic Province) to Cape Arago, Oregon. Observations were lumped by season for each species, with winter defined as starting January 1. Most species of heterobranchs in the region hatch as planktotrophic veliger larvae from their egg masses after an embryonic period of 1-2 weeks, and then have obligatory planktonic periods of at least 1 month (Hadfield andSwitzer-Dunlap 1984, Goddard 2004).                                                   Figure S68. Multivariate Ocean Climate Indicator (MOCI) for northern California, from winter 1991 to winter 2017. MOCI synthesizes coastal ocean and atmospheric conditions as well as regional climate indices like ENSO and PDO (García-Reyes and Sydeman 2017). Positive (red) values indicate seasons that are warm and with weak upwelling, while negative (blue) values are cold conditions with strong upwelling. The 2014−2016 period shows many (noncontinuous) seasons with warm conditions, only comparable to ENSO years in magnitude, although more persistent than ENSO. Warm conditions were broken by quasi-normal upwelling season conditions in northern California, but were more persistent in central and southern California.