Mutualisms play a critical role in ecological communities, however the importance and prevalence of mutualistic associations can be modified by external stressors. On coral reefs, elevated sediments are a major stressor, reducing the health of corals and damaging reef resilience. Here, we investigated the influence of sediment stress on the mutualistic relationship between small damselfishes (Dascyllus aruanus and Pomacentrus moluccensis) and their coral host (Pocillopora damicornis). In an aquaria experiment, corals were exposed to sedimentation rates of ~100 mg cm-2 day-1, with and without symbiont fish to test whether: (1) fishes influence the accumulation of sediments on coral hosts, and (2) fishes moderate partial colony mortality and/or condition. Colonies with fishes accumulated much less sediment compared to colonies without fishes, and this effect was strongest for colonies with D. aruanus (five-fold less sediment than controls) as opposed to P. moluccensis (two-fold less sediment than controls). Colonies with symbiont fishes also had up to 10-fold less sediment-induced partial mortality, as well as higher chlorophyll and protein concentrations. These results demonstrate that fish mutualisms vary in the strength of their benefits and indicates that some mutualistic or facilitative interactions might become more important for species health and resilience as stress levels increase.
Datasets were collected through a combination of field and aquaria experiments on fish behaviour and coral physiology.
Partial colony mortality values for corals in the sediment aquaria experiment
The "colonymortality.csv" data file includes the proportion of the whole colony, P. damicornis, partial mortality at the end of the sediment experiment (28 days treatment exposure). For every coral colony, the sediment and fish treatments are listed, as well as the proportion of colony mortality (propmortality), at the "END" of the experiment. Note that a very small constant (0.001) was added to every colony's proportion mortality, to allow for analysis using a beta regression model (binomial distribution, bounded between 0 and 1).
colonymortality.csv
Tissue values (protein and tissue biomass) sediment aquaria experiment
The "sedaqu.csv" datafile contains the proportion of colony mortality (whole colony) and tissue components of total proteins (protein), and tissue biomass (afdw) of the sample P. damicornis fragments sampled at the beginning ("START" - day 0 after a week of acclimation) and "END" (28 days of treatment exposure) of the sediment experiment in aquaria. For every coral, the phase of the experiment and sediment and fish treatments are listed. All values in the protein and afdw data are expressed per cm2 of surface area.
sedaqu.csv
Chlorophyll tissue components and values for sediment aquaria experiment
The "sedchl.csv" datafile contains the data on the total chlorophyll (A and C2) of the sample P. damicornis fragments sampled at the beginning ("START" - day 0 after a week of acclimation) and "END" (28 days of treatment exposure) of the sediment experiment in aquaria. For every coral, the phase of the experiment and sediment and fish treatments are listed. All values in the chlorophyll data are expressed per cm2 of surface area. Additional information regarding the different chlorophyll components (A and C2) are included in the data sheet.
sedchl.csv
Supplementary data on Sediment Traps
The "sedtrapsgrain.csv" data file contains supplementary data on the total sediment and sediment grain sizes (small (<125 µm), medium (125-500 µm), and large (500-4000 µm) collected from 6 sites around the Palm Islands, QLD, using sediment traps (simple tube traps).
sedtrapsgrain.csv
Supplementary data on Vacuum collected sediments
The "vacuumseds.csv" data file contains supplementary data on the total sediment collected from 4 sites around the Palm Islands, QLD, using a submersable sediment vacuum.
vacuumseds.csv
Supplementary data on suspended sediment in the sediment aquaria experiment
The "suspendedsediment_aquaria.csv" data file contains supplementary data on the suspended sediment collected 5 cm above a subset of sample P. damicornis colonies in the sediment aquaria experiment. These samples (~45-50ml) were collected 1 hour after daily sediment addition using a syringe.
suspendedsediment_aquaria.csv
Damselfish position around host coral colonies in the sediment aquaria experiment
The "fishpositionaquaria.cvs" data file contains data regarding the diurnal and nocturnal positions of the two damselfish species, Dascyllus aruanus and Pomacentrus moluccensis, during the sediment aquaria experiment. The position of each fish during spot checks are listed in the data file and these positions converted to proportions are also listed on the data file.
fishpositionaquaria.csv
Sediment on coral in the sediment aquaria experiment
The "coralsed.csv" data file contains data on the total sediment and sediment grain sizes (small (<125 µm), medium (125-500 µm), and large (500-4000 µm) collected from the coral colonies in the sediment aquaria experiment, after 28 days of treatment exposure. The sediment and fish treatments are listed for every coral colony.
coralsed.csv
Tissue values (protein and tissue biomass) sediment aquaria experiment
The "sedaqu.csv" datafile contains the proportion of colony mortality (whole colony) and tissue components of total proteins (protein), and tissue biomass (afdw) of the sample P. damicornis fragments sampled at the beginning ("START" - day 0 after a week of acclimation) and "END" (28 days of treatment exposure) of the sediment experiment in aquaria. For every coral, the phase of the experiment and sediment and fish treatments are listed. All values in the protein and afdw data are expressed per cm2 of surface area.
sedaqu.csv