Coral Community Structure and Recruitment in Seagrass Meadows

Abstract

Coral communities are increasingly found to populate non-reef habitats prone to high environmental variability. Such sites include seagrass meadows, which are generally not considered optimal habitats for corals as a result of limited suitable substrate for settlement and substantial diel and seasonal fluctuations in physicochemical conditions relative to neighboring reefs. Interest in understanding the ability of corals to persist in non-reef habitats has grown, however little baseline data exists on community structure and recruitment of scleractinian corals in seagrass meadows. To determine how corals populate seagrass meadows, we surveyed the established and recruited coral community over 25 months within seagrass meadows at Little Cayman, Cayman Islands. Simultaneous surveys of established and recruited coral communities at neighboring back-reef sites were conducted for comparison. To fully understand the amount of environmental variability to which corals in each habitat were exposed, we conducted complementary surveys of physicochemical conditions in both seagrass meadows and back-reefs. Despite overall higher variability in physicochemical conditions, particularly pH, compared to the back-reef, 14 coral taxa were capable of inhabiting seagrass meadows, and multiple coral families were also found to recruit to these sites. However, coral cover and species diversity, richness, and evenness were lower at sites within seagrass meadows compared to back-reef sites. Although questions remain regarding the processes governing recruitment, these results provide evidence that seagrass beds can serve as functional habitats for corals despite high levels of environmental variability and suboptimal conditions compared to neighboring reefs.

Mangrove lagoons of the Great Barrier Reef support coral populations persisting under extreme environmental conditions

“…Further research is required to establish whether the reduction in species diversity results from a genetic or environmental bottleneck. Environmental filtering was postulated as one potential reason why some coral taxa were absent from a highly variable inshore habitat of the Cayman Islands (Lohr et al 2017). Presence of both broadcast and spawning coral species suggests that reproductive mode does not explain the presence or absence of coral species from the mangrove lagoon habitats examined here.…”

The Future of Coral Reefs Subject to Rapid Climate Change: Lessons from Natural Extreme Environments

“…However, corals can recruit into seagrass systems; for example in the Cayman Islands where 14 coral taxa (primarily P. astreoides and Siderastrea sp.) were found to recruit into seagrass beds (Lohr et al, 2017). The ability of seagrasses to moderate the local seawater carbonate chemistry has resulted in an increased interest in their role as a coral habitat and potential coral refugia, although, the latter role is still unclear.…”

Diminishing potential for tropical reefs to function as coral diversity strongholds under climate change conditions

“…was predicted to become a potential future coral biodiversity hotspot. However, most of the area is characterized by unconsolidated sand patches, seagrass meadows and extreme environmental conditions, such as high salinity conditions, which limits the settlement and survival of coral species in the area (Bauman et al, 2015;Lohr et al, 2017). Whether these locations can function as a viable future coral stronghold under continued climate change pressure remains to be seen.…”