MARINE AND TERRESTRIAL SEDIMENT ON ALGAL TURF LIMITS HERBIVORY PRESSURE AND SPECIES RICHNESS

When disturbance leads to coral mortality,  herbivorous fish provide strong top-down control that maintains turf algae in a short healthy state, favoring coral recruitment and recovery. While it is well known that marine sediment deters fish herbivory, the effect of terrestrial sediment, which is increasing on coral reefs due to climate change and coastal development, remains understudied. This study examines the effect of marine and terrestrial sediment on fish herbivory rate on algal turf. We compared three sites (n=10 plots per site) in Mo’orea, French Polynesia with different turf heights (LME, p<0.001) and sediment depths (p<0.0001). Total fish herbivory rates, quantified from video recordings of bite rates on replicate experimental plots, did not vary between sites (Kruskal-Wallis, p>0.05). Rather, bite rates for individual species as well as the species richness of the fish taking bites differed across sites. Richness and herbivory rates were highest where sediment and turf were lowest. Both herbivory and fish diversity declined at the site with marine sediment and long turf and were lowest by far at the site with terrestrial sediment and long turf. Overall, results showed that terrestrial sediment deterred herbivory more than marine sediment. Thus, increases in sedimentation, particularly of terrestrial sediments, associated with climate change could further degrade coral reefs by decreasing total herbivory and the species richness of the herbivore community, likely further inhibiting coral recovery.

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Primary Presenter: Zuri Murph, Hampton University (zuri.murph@my.hamptonu.edu)

Authors:

Zuri Murph, Hampton Univerisity  (zuri.murph@my.hamptonu.edu)

Amarie Strong, UCLA  (amarie.strong@gmail.com)

Alondra Gallegos, TDP  (alondragalle@g.ucla.edu)

TaVon Palmer, TDP  (chc70fsu75@gmail.com)