Inshore, turbid coral reefs from northwest Borneo exhibiting low diversity, but high cover show evidence of resilience to various environmental stressors
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Abstract
For reefs in SE Asia the synergistic effects of rapid land-development, insufficient environmental policies and a lack of enforcement has led to poor water quality and compromised coral health from increased sediment and pollution. Those inshore turbid coral reefs, subject to significant sediment inputs, may also inherit some resilience to the effects of thermal stress and coral bleaching. We studied the inshore turbid reefs near Miri, in northwest Borneo, through a comprehensive assessment of coral cover, health and function in addition to quantifying sediment-related parameters. Although Miri Reefs had comparatively low coral species diversity, dominated by massive and encrusting forms of Diploastrea, Porites, Montipora, Favites, Dipsastrea and Pachyseris, they were characterised by a healthy cover ranging from 22-39%. We found a strong inshore to offshore gradient in hard coral cover, diversity and community composition as a direct result of spatial differences in sediment but over scales of <10 km. As well as distance to shore, we included other environmental variables like reef depth and sediment accumulation/size that explained 62.5% of variation in benthic composition among sites. None of the reefs showed evidence of coral disease and relatively low prevalence of compromised health signs including bleaching (6.7%), bioerosion (6.6%), pigmentation (2.2%), scars (1.1%) and mucus production (0.5%). There were, however, seasonal differences in bioerosion rates which increased five-fold after the 2017 wet season. Tagged colonies of Diploastrea and Pachyseries showing partial bleaching in 2016, had fully recovered by 90-100% the following year. Differences in measures of coral function like that of symbiont density and chlorophyll a for Montipora, Pachyseris and Acropora were not detected among sites. This study provides further evidence that turbid coral reefs exposed to seasonally elevated sediment loads can exhibit relatively high coral cover and be resilient to disease and elevated sea surface temperatures.
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2018. Inshore, turbid coral reefs from northwest Borneo exhibiting low diversity, but high cover show evidence of resilience to various environmental stressors. PeerJ Preprints 6:e27422v1 https://doi.org/10.7287/peerj.preprints.27422v1note This preprint is not peer-reviewed. You may wish to reference the subsequent peer-reviewed version of this article.
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This is a submission to PeerJ for review.
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Photographs of the 5 stages of symbiont cell degradation. A. Symbiont cells on the haemocytometer, B. stage 1, C. stage 2, D. stage 3, E. stage 4, and F. stage 5
Average monthly in water temperature (oC) at Eve’s Garden (EG) and Anenome’s Garden (AG) from September 2016 until May 2017
Average daily turbidity (FTU) measured over 8 days in September 2016 at Eve’s Garden and Siwa Reef
Average prevalence (%) of the four types of bleaching patterns observed at the three surveyed sites (EG = Eve’s Garden, AG = Anenome’s Garden, Siwa) following the dry and wet seasons
Average density for A. symbiont and B. chlorophyll a pigment for three coral species (Acropora, Montipora, Pachyseris) sampled in May 2017 at the three surveyed sites (EG = Eve’s Garden, AG = Anenome’s Garden, Siwa)
Average percentage of cells for each grade of symbiont (1= healthy, 2= initiation of degradation, 3= in degradation process, 4= degraded and dead cell, 5= totally degraded) for A. each site surveyed (
DbRDA plots based on the DistLM with AIC model selection with the three significant (p<0.05) drivers of coral health for A. scars, B. pigmentation, C. bioerosion, and D. bleaching. The bubble sizes represent prevalence percentages with each bubble represe
DbRDA plots based on the DistLM with AIC model selection with all the sediment drivers for A. scars, B. pigmentation, C. bioerosion, and D. bleaching. Note that only course and fines are significantly (p<0.05) explaining 18% of the variation in coral heal
Additional Information
Competing Interests
The authors declare that they have no competing interests.
Author Contributions
Christina Brown performed the experiments, analyzed the data, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Nicola Browne conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Jennifer L McIlwain performed the experiments, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Jens Zinke contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Field Study Permissions
The following information was supplied relating to field study approvals (i.e., approving body and any reference numbers):
Field experiments were approved by the Sarawak Forestry Commission
Data Deposition
The following information was supplied regarding data availability:
Included in the Supplementary section of this submission
Funding
This work was supported by the National Geographic Society Research Grant (No. CP-025ER-17), Curtin Sarawak Research Institute and the German Acdemic Exchange Service (No. 57318354). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.