Biology subjects

Valdivia, A.

Publications and source records attributed to Valdivia, A..

2 recordsLinked to original sources

bioRxiv2021

Twenty years of change in benthic communities across the Belizean Barrier Reef

Disease, ocean warming, and pollution have caused catastrophic declines in the cover of living coral on reefs across the Caribbean. Subsequently, reef-building corals have been replaced by invertebrates and macroalgae, leading to changes in ecological functioning. We describe changes in benthic community composition and cover at 15 sites across the Belizean Barrier Reef (BBR) following numerous major disturbances--bleaching, storms, and disease outbreaks--over the 20-year period 1997-2016. We tested the role of potential drivers of change on coral reefs, including local human impacts and ocean temperature. From 1997 to 2016, mean coral cover significantly declined from 26.3% to 10.7%, while macroalgal cover significantly increased from 12.9% to 39.7%. We documented a significant decline over time of the reef-building corals Orbicella spp. and described a major shift in benthic composition between early sampling years (1997-2005) and later years (2009-2016). The covers of hard-coral taxa, including Acropora spp., M. cavernosa, Orbicella spp., and Porites spp., were negatively related to marine heatwave frequency. Only gorgonian cover was related, negatively, to our metric of the magnitude of local impacts (the Human Influence Index). Changes in benthic composition and cover were not associated with local protection or fishing. This result is concordant with studies throughout the Caribbean that have documented living coral decline and shifts in reef-community composition following disturbances, regardless of local fisheries restrictions. Our results suggest that benthic communities along the BBR have experienced disturbances that are beyond the capacity of the current management structure to mitigate. We recommend that managers devote greater resources and capacity to enforce and expand existing marine protected areas and that government, industry, and the public act to reduce global carbon emissions.

ecology↗

bioRxiv2018

Marine mammals and sea turtles listed under the U.S. Endangered Species Act are recovering

The U.S. Endangered Species Act (ESA) is the worlds strongest environmental law protecting imperiled plants and animals, and a growing number of marine species have been protected under this law as extinction risk in the oceans has increased. Marine mammals and sea turtles comprise 36% of the 161 ESA-listed marine species, yet analyses of recovery trends after listing are lacking. Here we gather the best available annual population estimates for all marine mammals (n=33) and sea turtles (n=29) listed under the ESA as species. Of these, we quantitatively analyze population trends, magnitude of population change, and recovery status for representative populations of 23 marine mammals and 9 sea turtles, which were listed for more than five years, occur in U.S. waters, and have data of sufficient quality and span of time for trend analyses. Using generalized linear and non-linear models, we found that 78% of marine mammals (n=18) and 78% of sea turtles (n=7) significantly increased after listing; 13% of marine mammals (n=3) and 22% of sea turtles (n=2) showed non-significant changes; while 9% of marine mammals (n=2), but no sea turtles declined after ESA protection. Overall, species with populations that increased in abundance were listed for 20 years or more (e.g., large whales, manatees, and sea turtles). Conservation measures triggered by ESA listing such as ending exploitation, tailored species management, and fishery regulations, among others, appear to have been largely successful in promoting species recovery, leading to the delisting of some species and to increases in most. These findings underscore the capacity of marine mammals and sea turtles to recover from substantial population declines when conservation actions under the ESA are implemented in a timely and effective manner.

ecology↗