The effects of multiple anthropogenic stressors on coral reef communities

Recent meta-analyses suggest that multiple stressors most often interact, with combined effects that are mitigated in autotrophs and exacerbated at higher trophic levels(1,2). In coral reef ecosystems worldwide, coastal development drives nutrient loading and sedimentation(3,4), co-occurring stressors that have each been implicated in a variety of negative effects on corals(5). Studies have shown that increased nutrient levels can retard coral growth, limit reproduction, and increase the probability of algal phase shifts(6,7,8). Additionally, observed effects of nutrients on corals have shown considerable variation among species(9,10), potentially scaling up to affect coral competition and relative abundance. Similarly, sedimentation has been shown to inhibit feeding, waste removal and limestone secretion in corals, thus affecting growth and survival(9).

 

Recent laboratory studies have shown negative synergistic effects of nutrients and sediments on fertilization in certain scleractinian corals(10), however, no published studies have examined the combined effects of these stressors on corals in the field. In turn, the possible adverse effects of nutrient enrichment and sedimentation remain largely unknown. With my proposed research, I will quantify both the interaction between and species-specific effects of nutrient loading and sedimentation with respect to coral growth, survivorship and competition with macroalgae. I will also quantify the effects of these environmental stressors on benthic invertebrate and reef fish assemblages on patch reefs through surveys and experiments. I expect that nutrient loading and sedimentation will have negative synergistic effects on coral growth, survival and competition with algae. I also predict that these stressors will differentially affect different guilds, causing more pronounced, short-term shifts in species assemblages among higher trophic-level organisms (e.g. reef fishes).

 

This work will provide novel insights concerning environmental stressors in nature by empirically testing theories concerning stressor interactions in autotrophs and combined stressor effects across trophic levels and clarifying the mechanisms by which environmental stressors give rise to community-level effects. Specifically, this work will improve understanding of anthropogenic effects on ecologically and economically critical coral reefs, which support valuable fisheries and provide storm surge protection worldwide.

 

1. Crain, CM et al. (2008) Ecol. Lett.. 11: 1304-1315. ; 2. Darling, ES and Cote, IM (2008) Ecol. Lett. 11: 1278-1286. 3. Cloern, JE (2001) Mar. Ecol.-Prog. Ser. 210: 223–253. 4. Orth, RJ et al. (2006) Bioscience 56: 987-996. ; 5. Cortes and Risk (1985). Bull. Mar. Sci., 36:339-365.; 6. Koop et al. (2001). Mar. Pollut. Bull., 42:91-120.; 7. Small and Adey. (2001). Ecol. Eng., 16:443-457.; 8. Smith et al. (2001). Coral Reefs, 19:332-342.; 9. Barnes. (1987). Invertebrate Zoology 5th Edition.; 10. Humphrey et al. (2008). Coral Reefs, 27:837–850

 

Project Information
Researchers: 
Start Date: 
2010