Edwin A. Hernández-Delgado

Demographics of bleaching in a major Caribbean reef-building coral: Montastraea annularis

Mass bleaching events have become a major cause of coral decline at a global scale. In the summer/fall of 2005 the northeastern Caribbean experienced a record-breaking sea surface warming that resulted in a prolonged mass bleaching event and significant percent coral cover decline of the principal Caribbean reef-building coral Montastraea annularis. In this study, we measured changes in the vital rates of a M. annularis population before, during, and after the 2005 mass bleaching event; stochastically projected the population with different bleaching regimes using a 100 year horizon; and quantified the population level effect of the bleaching event using a life table response experiment. Size-based transition matrices from 2001–2009 were constructed following 399 colonies through time in 17 permanent photo-transects located in Culebra Island, Puerto Rico. Temporal variation in the population growth rate indicates the population (1) was in demographic equilibrium before the event (λ ≈ 1.0), (2) suffered a significant decline in growth rate for two consecutive years after the event (λ < 1.0), and (3) demographically recovered three years after the event (λ ≈ 1.0). Partial tissue mortality due to bleaching caused dramatic colony fragmentation that resulted in a population made up almost entirely of small colonies by 2007 (97% were <50 cm2). The stochastic simulation indicates that an annual probability of bleaching in excess of 6% would result in a decreasing population (λs < 1.0) with a reduction of more than 54% in colony abundance after 100 years of projection. The life table response experiments reveal that most of the effect that bleaching had on the population growth rate comes from changes in the survivorship of small colonies. Recent trends in population decline, as well as the life history traits of M. annularis, suggest that recovery of affected populations by sexual recruitment alone is unlikely. Our findings indicate that survival of small colonies will determine the viability of the M. annularis populations within the context of rising sea surface temperatures. We conclude that the demography of M. annularis is highly susceptible to bleaching and that its viability is seriously compromised under the predicted global warming scenarios.

Watershed- and island wide-scale land cover changes in Puerto Rico (1930s–2004) and their potential effects on coral reef ecosystems

Anthropogenically enhanced delivery of sediments and other land-based sources of pollution represent well-recognized threats to nearshore coral reef communities worldwide. Land cover change is commonly used as a proxy to document human-induced alterations to sediment and pollutant delivery rates to coral reef bearing waters. In this article, land cover change was assessed for a 69-km(2) watershed in Puerto Rico between 1936 and 2004 by aerial photograph interpretation. Forests and sugar cane fields predominated from 1936 through the late 1970s, but while cropland dipped to negligible levels by 2004, net forest cover doubled and built-up areas increased tenfold. The watershed-scale land cover changes documented here mimicked those of the entire Puerto Rican landmass. Sediment yield predictions that rely on the sort of land cover changes reported here inevitably result in declining trends, but anecdotal and scientific evidence in the study watershed and throughout Puerto Rico suggests that sediment and pollutant loading rates still remain high and at potentially threatening levels. The simultaneous reduction in living coral cover that accompanied reforestation and urbanization patterns since the 1970s in our study region is discussed here within the context of the following non-mutually exclusive potential explanations: (a) the inability of land cover change-based assessments to discern spatially-focused, yet highly influential sources of sediment; (b) the potentially secondary role of cropland and forest cover changes in influencing nearshore coral reef conditions relative to other types of stressors like those related to climate change; and (c) the potentially dominant role that urban development may have had in altering marine water quality to the extent of reducing live coral cover. Since identification of the causes for coral reef degradation has proven elusive here and elsewhere, we infer that coral reef management may only be effective when numerous land- and marine-based stressors are simultaneously mitigated.

An Interdisciplinary Erosion Mitigation Approach for Coral Reef Protection – A Case Study from the Eastern Caribbean

Carlos E. Ramos-Scharron1,2, Juan M. Amador3 and Edwin A. Hernandez-Delgado4,5 1Island Resources Foundation, 2Department of Geography & the Environment, the University of Texas-Austin, 3Greg L. Morris Engineering COOP, 4Center for Applied Tropical Ecology and Conservation, University of Puerto Rico-Rio Piedras, 5Caribbean Coral Reefs Institute, University of Puerto Rico-Mayaguez, 1US Virgin Islands 2USA 3,4,5Puerto Rico

Review of Echinoderm Research in Puerto Rico, with the Focus on Biological and Ecological Aspects

Echinoderms are functionally important components on coral reef ecosystems. Coral reef communities on the insular shelf of Puerto Rico have been studied, especially in the southwest region of the island. However, many of these reef surveys do not include the abundance of echinoderms. Echinoderm research carried out in Puerto Rico has mostly focused on ecological aspects. During 2006, Benavides revised the taxonomic list of shallower water Echinodermata in Puerto Rico. She identified a total of 108 echinoderm species (6 crinoid species, 14 asteroid species, 44 ophuiroid species, 15 echinoid species and 29 holothuroid species). In addition, Hernandez-Delgado has carried out multiple studies describing echinoderm distribution around Puerto Rico, especially in areas where research has been limited. The University of Puerto Rico (UPR), an important research center, has supported multiple studies related to echinoderms. The laboratory of Jose Garcia-Arraras in the Department of Biology at UPR has done comprehensive work on the process of intestinal regeneration in the sea cucumber Holothuria (Selenkothuria) glaberrima (Selenka); in the hope that researchers would start considering echinoderms as model systems for pharmacological studies in muscle development and regeneration. Cameron and Williams et al. have described the reproduction patterns, larval distribution/settlement and recruitment of different sea urchin species in La Parguera, Puerto Rico. Other ecological studies such as bioerosion and echinoderm diversity are also discussed. In this chapter we present a comprehensive historical account of echinoderm research in Puerto Rico. We also make recommendations for future research.

Twentieth century warming of the tropical Atlantic captured by Sr‐U paleothermometry

Coral skeletons are valuable archives of past ocean conditions. However, interpretation of coral paleotemperature records is confounded by uncertainties associated with single element-ratio thermometers, including Sr/Ca. A new approach, Sr-U, uses U/Ca to constrain the influence of Rayleigh fractionation on Sr/Ca [DeCarlo et al., 2016]. Here, we build on the initial Pacific Porites Sr-U calibration to include multiple Atlantic and Pacific coral genera from multiple coral reef locations spanning a temperature range of 23.15-30.12 °C. Accounting for the wintertime growth cessation of one Bermuda coral, we show that Sr-U is strongly correlated with the average water temperature at each location (r2 = 0.91, P < 0.001, n = 19). We applied the multi-species spatial calibration between Sr-U and temperature to reconstruct a 96-year long temperature record at Mona Island, Puerto Rico using a coral not included in the calibration. Average Sr-U derived temperature for the period 1900-1996 is within 0.12 °C of the average instrumental temperature at this site and captures the 20th century warming trend of 0.06 °C per decade. Sr-U also captures the timing of multi-year variability but with higher amplitude than implied by the instrumental data. Mean Sr-U temperatures and patterns of multi-year variability were replicated in a second coral in the same grid box. Conversely, Sr/Ca records from the same two corals were inconsistent with each other and failed to capture absolute sea temperatures, timing of multi-year variability or the 20th century warming trend. Our results suggest that coral Sr-U paleothermometry is a promising new tool for reconstruction of past ocean temperatures.

Marine Managed Areas and Associated Fisheries in the US Caribbean

The marine managed areas (MMAs) of the U.S. Caribbean are summarized and specific data-rich cases are examined to determine their impact upon fisheries management in the region. In this region, the productivity and connectivity of benthic habitats such as mangroves, seagrass and coral reefs is essential for many species targeted by fisheries. A minority of the 39 MMAs covering over 4000km(2) serve any detectable management or conservation function due to deficiencies in the design, objectives, compliance or enforcement. Fifty percent of the area within MMA boundaries had no-take regulations in the U.S. Virgin Islands, while Puerto Rico only had 3%. Six case studies are compared and contrasted to better understand the potential of these MMAs for fisheries management. Signs of success were associated with including sufficient areas of essential fish habitat (nursery, spawning and migration corridors), year-round no-take regulations, enforcement and isolation. These criteria have been identified as important in the conservation of marine resources, but little has been done to modify the way MMAs are designated and implemented in the region. Site-specific monitoring to measure the effects of these MMAs is needed to demonstrate the benefits to fisheries and gain local support for a greater use as a fisheries management tool.

Effects of Changing Weather, Oceanographic Conditions, and Land Uses on Spatio-Temporal Variation of Sedimentation Dynamics along Near-Shore Coral Reefs

Sedimentation is a critical threat to coral reefs worldwide. Major land use alteration at steep, highly erodible semi-arid islands accelerates the potential of soil erosion, runoff, and sedimentation stress to nearshore coral reefs during extreme rainfall events. The goal of this study was to assess spatio-temporal variation of sedimentation dynamics across nearshore coral reefs as a function of land use patterns, weather and oceanographic dynamics, to identify marine ecosystem conservation strategies. Sediment was collected at a distance gradient from shore at Bahia Tamarindo (BTA) and Punta Soldado (PSO) coral reefs at Culebra Island, Puerto Rico. Sediment texture and composition were analyzed by dry sieving and loss-on-ignition techniques, and were contrasted with environmental variables for the research period (February 2014 to April 2015). Rainfall and oceanographic data were analyzed to address their potential role on affecting sediment distribution with BEST BIO-ENV, RELATE correlation, and linear regression analysis. A significant difference in sedimentation rate was observed by time and distance from shore (PERMANOVA, p<0.0100), mostly attributed to higher sediment exposure at reef zones closer to shore due to strong relationships with coastal runoff. Sedimentation rate positively correlated with strong rainfall events (Rho= 0.301, p=0.0400) associated with storms and rainfall intensity exceeding 15 mm/hr. At BTA, sediment deposited were mostly composed of sand, suggesting a potential influence of resuspension produced by waves and swells. In contrast, PSO sediments were mostly composed of silt-clay and terrigenous material, mainly attributed to a deforestation event that occurred at adjacent steep sub-watershed during the study period. Spatial and temporal variation of sedimentation pulses and terrigenous sediment input implies that coral reefs exposure to sediment stress is determined by local land use patterns, weather, and oceanographic dynamics. Comprehensive understanding of sediment dynamics and coastal ecosystem interconnectivity is fundamental to implement integrated and adaptive management strategies aimed to promote sustainable development at watershed and island wide-scale to fully mitigate terrigenous sediment impact to marine ecosystems. Furthermore, decision-making processes and policy needs to address sedimentation stress in the context of future climate to reduce land-based threats and strengthen coral reef resilience.