Water Quality Anomalies following the 2017 Hurricanes in Southwestern Puerto Rico: Absorption of Colored Detrital and Dissolved Material

Absorption of colored dissolved organic matter or detrital gelbstoff (aCDOM/ADG) and light attenuation coefficient (Kd490) parameters were studied at La Parguera Natural Reserve in southwestern Puerto Rico, before and following Hurricanes Irma (6–7 September) and María (20–21 September) in 2017. Water quality assessments involving Sentinel 3A ocean color products and field sample data was performed. The estimated mean of ADG in surface waters was calculated at >0.1 m−1 with a median of 0.05 m−1 and aCDOM443 ranged from 0.0023 to 0.1121 m−1 in field samples (n=21) in 2017. Mean ADG443 values increased from July to August at 0.167 to 0.353 m−1 in September–October over Turrumote reef (LP6) with a maximum value of 0.683 m−1. Values above 0.13 m−1 persisted at offshore waters off Guánica Bay and over coral reef areas at La Parguera for over four months. The ADG443 product presented values above the median and the second standard deviation of 0.0428 m−1 from September to October 2017 and from water sample measurement on 19 October 2017. Mean Kd490 values increased from 0.16 m−1 before hurricanes to 0.28 right after Hurricane Irma. The value remained high, at 0.34 m−1, until October 2017, a month after Hurricane María. Analysis of the Sentinel (S3) OLCI products showed a significant positive correlation (rs = 0.71, p = 0.0005) between Kd490_M07 and ADG_443, indicating the influence of ADG on light attenuation. These significant short-term changes could have ecological impacts on benthic habitats highly dependent on light penetration, such as coral reefs, in southwestern Puerto Rico.

Comparison of Satellite-Based Sea Surface Temperature to In Situ Observations Surrounding Coral Reefs in La Parguera, Puerto Rico

Coral reefs are among the most biologically diverse ecosystems on Earth. In the last few decades, a combination of stressors has produced significant declines in reef expanse, with declining reef health attributed largely to thermal stresses. We investigated the correspondence between time-series satellite remote sensing-based sea surface temperature (SST) datasets and ocean temperature monitored in situ at depth in coral reefs near La Parguera, Puerto Rico. In situ temperature data were collected for Cayo Enrique and Cayo Mario, San Cristobal, and Margarita Reef. The three satellite-based SST datasets evaluated were NOAA’s Coral Reef Watch (CoralTemp), the UK Meteorological Office’s Operational SST and Sea Ice Analysis (OSTIA), and NASA’s Jet Propulsion Laboratory (G1SST). All three satellite-based SST datasets assessed displayed a strong positive correlation (>0.91) with the in situ temperature measurements. However, all SST datasets underestimated the temperature, compared with the in situ measurements. A linear regression model using the SST datasets as the predictor for the in situ measurements produced an overall offset of ~1 °C for all three SST datasets. These results support the use of all three SST datasets, after offset correction, to represent the temperature regime at the depth of the corals in La Parguera, Puerto Rico.

Growth dynamics in Acropora cervicornis and A. prolifera in southwest Puerto Rico

Natural population recovery of Acropora palmata, A. cervicornis and their hybrid, Acropora prolifera, have fluctuated significantly after their Caribbean-wide, disease-induced mass mortality in the early 1980s. Even though significant recovery has been observed in a few localities, recurrent disease outbreaks, bleaching, storm damage, local environmental deterioration, algae smothering, predation, low sexual recruitment and low survivorship have affected the expected, quick recovery of these weedy species. In this study, the status of three recovering populations of A. cervicornis and two of A. prolifera were assessed over one year using coral growth and mortality metrics, and changes in their associated algae and fish/invertebrate communities in three localities in the La Parguera Natural Reserve (LPNR), southwest coast of Puerto Rico. Five branches were tagged in each of 29, medium size (1–2 m in diameter) A. cervicornis and 18 A. prolifera colonies in the Media Luna, Mario and San Cristobal reefs off LPNR. Branches were measured monthly, together with observations to evaluate associated disease(s), algae accumulation and predation. A. cervicornis grew faster [3.1 ± 0.44 cm/month (= 37.2 cm/y)] compared to A. prolifera [2.6 ± 0.41 cm/month (= 31.2 cm/y)], and growth was significantly higher during Winter-Spring compared to Summer-Fall for both taxa (3.5 ± 0.58 vs. 0.53 ± 0.15 cm/month in A. cervicornis, and 2.43 ± 0.71 vs. 0.27 ± 0.20 cm/month in A. prolifera, respectively). Algal accumulation was only observed in A. cervicornis, and was higher during Spring-Summer compared to Fall-Winter (6.1 ± 0.91 cm/month and 3.8 ± 0.29 cm/month, respectively, (PERMANOVA, df = 2, MS = 10.2, p = 0.37)). Mortality associated with white band disease, algae smothering and fish/invertebrate predation was also higher in A. cervicornis and varied among colonies within sites, across sites and across season. The balance between tissue grow and mortality determines if colonies survive. This balance seems to be pushed to the high mortality side often by increasing frequency of high thermal anomalies, inducing bleaching and disease outbreaks and other factors, which have historically impacted the natural recovery of these taxa in the La Parguera Natural Reserve in Puerto Rico and possibly other areas in the region. Overall, results indicate variability in both growth and mortality rates in both taxa across localities and seasons, with A. cervicornis showing overall higher mortalities compared to A. prolifera.

Associated organisms inhabiting the calcareous spongeClathrina luteain La Parguera Natural Reserve, Puerto Rico

ABSTRACTSponges provide an array of ecological services and benefits for Caribbean coral reefs. They function as habitats for a bewildering variety of species, however limited attention has been paid in the systematics and distribution of sponge-associated fauna in the class Calcarea or for that matter of sponges in the Caribbean. The goal of this study was to characterize infaunal assemblages from a calcareous sponge,Clathrina lutea, across multiple reefs from the La Parguera Natural Reserve, Puerto Rico. The associated fauna from 43C. luteaspecimens yielded a total of 2,249 associated infauna distributed in seven invertebrate phyla. Arthropoda was the most abundant phylum accounting for 62.5% of total abundance, followed by Annelida (21.0%) and Nematoda (5.5%). Limited patterns of temporal or spatial variability were surmised due to the opportunistic sampling effort afforded to this investigation from the cryptic nature of this species. A concordance between our data set and those for the class Demospongiae were observed, with the most abundant associated fauna being copepods and polychaetes. However, when compared to other Calcarea, the present study found considerably more associated fauna.

Seasonal Net Ecosystem Metabolism of the Near-Shore Reef System in La Parguera, Puerto Rico

Changes in ocean chemistry as a direct response to rising atmospheric carbon dioxide (CO2) concentrations is causing a reduction of pH in the surface ocean. While the dynamics and trends in carbonate chemistry are reasonably constrained for open ocean waters, the ways in which ocean acidification (OA) manifests within the shallow near-shore waters, where coral reefs reside, is less understood. Constraining near-reef variability in carbonate chemistry and net ecosystem metabolic processes across diel, seasonal, and annual scales is important in evaluating potential biogeochemical thresholds of OA that could result in ecological community changes. The OA Test-Bed at La Parguera Marine Reserve in Puerto Rico provides long-term carbonate chemistry observations at high-temporal resolution within a Caribbean near-shore coral reef ecosystem. A 1-D model was developed using the carbon mass balance approach to yield information about net ecosystem production and calcification processes occurring in the water column adjacent to the reef. We present results of nine years of sustained monitoring at the Enrique mid-shelf forereef, which provides for the characterization of temporal dynamics in carbonate chemistry and net ecosystem metabolic processes encompassing near-shore and upstream locations. Results indicate that net heterotrophy and net dissolution dominate over most of the year, while net autotrophic conditions coupled with calcification dominated from only January to mid-April. The average carbonate dissolution rate observed during summer is estimated at −2.19 g CaCO3 m−2 day−1 and net community dissolution persists 76 % of the seasonal year despite the water column remaining super-saturated with respect to aragonite. This corresponds to −0.62 kg CaCO3 m−2 year−1, classifying the Enrique fore-reef and off-reef areas in a net dissolutional state. The combination of thermodynamically-driven depressed aragonite saturation state and high rates of respiration during the summer cause conditions that jeopardize the most soluble carbonate minerals and the free energy in the system for calcification. These data suggest that the reef area and associated ecosystems upstream of the sampling location are experiencing a net loss of CaCO3, possibly compromising coral ecosystem health and reef accretion processes necessary for maintenance as sea level increases. Resiliency from other climate-scale stressors including rising sea surface temperatures and coral bleaching is likely to be compromised in a system exhibiting net carbonate loss.