Nursing the ocean back to health

I came across a news article today about volunteer divers working towards restoring a coral reef recently damaged by a cruise ship anchor. This got me thinking about proactive ways people are working to restore ocean ecosystems: not just by reducing our negative impacts and hoping the ocean heals itself, but lending a helping hand - often in the early stages of organisms' lives. When much of ocean news is full of doom and gloom, it's helpful sometimes to remember that there are indeed success stories, and recovery is possible if we try hard enough.

Coral nurseries

Early life stages are the most treacherous for most organisms - so one tactic is to help struggling marine life through juvenile stages in safer conditions than the big bad world, and then release or replant them into the wild, larger and heartier and more likely to survive. Because corals are colonial organisms, fragments of adult colonies can be broken up and grown into new colonies. Coral nurseries typically take small fragments of corals and provide them a safe place larger by physically attaching them either to a hard substrate like concrete blocks, or even suspended ropes underwater. Usually, nurseries collect fragments that have broken naturally from storms, or after a disastrous event like a boat grounding. Leaving coral fragments where they lie after an event like this often leads to death of many fragments, because rubble gets tossed by waves and coral tissue abrades away, or fragments become smothered in sand.

Humans can help restore damaged reef areas by removing dislodged corals to a nursery area to grow, removing dead rubble that would act to damage living coral, and then replacing live corals into the damaged area. Coral nurseries have shown some signs of success, including spawning earlier this year by nursery-raised endangered Acropora corals. But, nurseries also require a lot of human-power to work, and no area of the ocean is now "safe" from ocean warming or acidification.

Artificial reefs

Another take on direct coral reef restoration is to encourage better coral growth in the existing environment, for example by providing space for corals to grow - the idea behind "Reefballs." Other methods include running low-wattage electricity through underwater structures, which directly stimulates coral growth. The idea here is that if corals grow faster than they do naturally, they might out-survive the threats like overfishing and climate change that are killing them off.

Mangrove replanting

Mangroves are coastal wetlands comprised of specialized trees that grow in saltwater. Tangled mangrove roots provide important nursery habitat for fish and other species; mangroves trap sediment runoff, protecting offshore coral reefs; mangroves can also act to buffer shorelines from storms. Despite their importance, mangroves are often destroyed for coastal development projects, or converted to aquaculture ponds. Restoring coastal water quality and ecosystem services often calls for restoring mangrove systems, which is often similar to coral restoration: planting seedlings. Unfortunately, some restoration projects struggle without proper scientific understanding (trees need to be planted in the right conditions), but with well-informed backing, these projects can also be successful.

Oyster hatching

Oysters act as ecosystem architects, similar to corals. Baby oysters preferentially recruit to adult oyster shells, and over time can form large reefs. Oysters are commercially and culturally important to humans, their reefs provide habitat for other marine life, and because they are filter feeders, oysters help maintain water quality where they occur. However, in parts of their range, oysters are in decline: in Chesapeake Bay, they only occur at about 1% of their natural abundance. Here is where restoration can work: by replacing harvested oyster beds with empty shells from commercial operations or geologic deposits, baby oyster spat have somewhere to recruit. Combined with rearing baby oysters on old shells in aquaria and outplanting, oyster reef restoration shows much promise of success. Restoring oyster reefs has the joint benefits of both helping a human-impacted species recover, and restoring water qualityand improving habitat for other marine species as well.

Sea turtle rearing

There are seven species of sea turtles around the world, and six are listed as threatened or endangered (the seventh isn't necessarily doing well, either - it just doesn't have enough information to be assessed). Turtles are often killed incidentally in fishing gears and they are their eggs are harvested off beaches where they nest (and in some cases, entire nesting populations have become extinct). Turtles have received a number of direct-intervention efforts, including redesigning longline hooks and shrimp trawl nets to be turtle-friendly. On many nesting beaches, humans directly protect sea turtle nests from poachers, accidental trampling, or predation by marking off or guarding nests, and/or removing eggs to a hatchery or protected beach area. Sea turtles are not just charismatic creatures: they are also important parts of a healthy marine ecosystem. For example, sea turtles are important grazers on sea grass beds; the loss of grazing animals like turtles and manatees leads to degradation of this critical habitat.

Can you think of other ways to take direct action for the oceans?

References

Rinkevich, B. (2005) Conservation of coral reefs through active restoration measures:  Recent approaches and last decade progress. Environ. Sci. Technol., 39, 4333-4342.

Bosire, J. O., Dahdouh-Guebas, F., Walton, M., Crona, B. I., Lewis III, R. R., Field, C., Cairo, J. G. & Koedam, N. (2008) Functionality of restored mangroves: a review. Aquatic Botany, 89, 251-259.

Beck, M. W., Brumbaugh, R. D., Airoldi, L., Carranza, A., Coen, L. D., Crawford, C., Edgar, G. J., Hancock, B., Kay, M. C., Lenihan, H. S., Luckenback, M. W, Toropova, C. L., Zhang, G. & Guo, X. (2011). Oyster reefs at risk and recommendations for conservation, restoration, and management. Bioscience, 61, 107-116.

Bjorndal, K. A., & Bolten, A. B. (2003). From ghosts to key species: restoring sea turtle populations to fulfill their ecological roles. Marine Turtle Newsletter, 100, 16-21.