Bocas del Toro Research Station

The rise of coral diseases has triggered a surge of interest in coral microbial communities. But to fully understand how the coral microbiome may cause or respond to disease, we must first understand structure and variation in the healthy coral microbiome. We used 16S rRNA sequencing to characterize the microbiomes of 100 healthy coral colonies from six Caribbean coral species (Acropora cervicornis, A. palmata, Diploria labyrinthiformis, Diploria strigosa, Porites astreoides and P. furcata) across four reefs and three time points over 1 year. We found host species to be the strongest driver of coral microbiome structure across site and time. Analysis of the core microbiome revealed remarkable similarity in the bacterial taxa represented across coral hosts and many bacterial phylotypes shared across all corals sampled. Some of these widespread bacterial taxa have been identified in Pacific corals, indicating that a core coral microbiome may extend across oceans. Core bacterial phylotypes that were unique to each coral were taxonomically diverse, suggesting that different coral hosts provide persistent, divergent niches for bacteria.

Cárdenas, P., Rapp, H. T., Schander, C. & Tendal, O. S. (2009). Molecular taxonomy and phylogeny of the Geodiidae (Porifera, Demospongiae , Astrophorida) – combining phylogenetic and Linnaean classification.— Zoologica Scripta, 39 , 89–106. According to the fossil records, the Geodiidae represents one of the oldest families of demosponges (Phylum Porifera). There are approximately 220 described extant species, geographically and bathymetrically widely distributed around the world. Species of this family all share a two‐layered cortex with ball‐shaped spicules called ‘sterrasters’ in the endocortex. However, molecular studies have questioned the monophyly of the group. Moreover, the evolutionary history and the intrafamily relationships of the Geodiidae are not fully resolved. Using a partial sequence of the cytochrome c oxidase subunit 1 (COI) gene and a partial sequence of the 28S rDNA gene (D1–D2 domains), we present the first molecular phylogeny focusing on this group. The congruent results from the two gene fragments suggest that (i) the Geodiidae is monophyletic, (ii) the Erylinae/Geodinae subdivision sensu Sollas, 1888 is valid and that (iii) Isops and Sidonops are junior synonyms of Geodia . The synonymization of Isops and Sidonops implies that the oscule/pore morphology as a diagnostic character should be abandoned. Geodia hentscheli nom. nov. has been given for Geodia mesotriaena ( Hentschel, 1929 ). This study served as the basis for a revised phylogenetic classification of the Geodiidae. Well‐supported clades led to the establishment of clade names following the PhyloCode . The Geodinae clade is strongly supported and notably composed of Depressiogeodia , Cydonium and Geodia . A morphological synapomorphy of Geodinae is the presence of euasters in the ectocortex. The Erylinae ( Erylus , Penares , Caminus and Pachymatisma ) form a strongly supported monophyletic group with three morphological synapomorphies: (i) loss of anatriaenes and protriaenes, (ii) microrhabds (or spherules) in the ectocortex and (iii) short‐shafted triaenes. The Erylus monophyly is ambiguous. Erylus species are distributed in three well‐supported clades. Finally, spicule homology in the cortex of the Geodiidae is discussed.

Abstract. Previous studies suggest that phototaxis in sponge larvae is generated by the bending of a tuft of long posterior cilia (LPC). The photoresponsiveness of these cilia is often assayed by examining their reaction to sudden changes in light intensity. Here, we document and describe the larvae of the tropical marine sponges Neopetrosia proxima and Xestospongia bocatorensis and examine the phototactic behavior of their larvae. Both species brood ovoid, tufted parenchymella larvae, clearly countering an earlier hypothesis that all petrosid sponges are oviparous. Larvae of N. proxima were positively phototactic and settled after 2 d, while larvae of X. bocatorensis were negatively phototactic and settled in as little as 4 h. In both species, LPC quickly responded to changes in the light intensity. When the light intensity is reduced, the larvae of N. proxima fold the cilia inwards immediately without beating, then flare them outwards, beating for a few seconds, and then gradually return to the neutral position while continuing to beat. In contrast, the larvae of X. bocatorensis flare the cilia outwards when the light intensity is reduced and fold them inwards when the light intensity is increased. Comparisons with reported ciliary responses to light for other species demonstrate that these responses do not show the hypothesized one‐to‐one correspondence with phototactic behaviors and are, therefore, of limited use in explaining the mechanisms that coordinate larval swimming.

Aquatic anthropogenic noise is on the rise, with growing concern about its impact on species that are sensitive to low-frequency sounds (e.g. most fish and invertebrates). We investigated whether the reef fish Halichoeres bivittatus living in both noisy and quiet areas had differing levels of baseline stress (measured as whole-body cortisol) and whether they would exhibit a physiological stress response when exposed to boat noise playbacks. While the playback experiments significantly increased cortisol levels in fish from our experiment compared to baseline levels, there were minimal pairwise differences across treatments and no difference in baseline stress for fish living in noisy vs. quiet areas. These results may be explained by low overall auditory sensitivity, habituation to a fairly noisy environment (due to biological sounds), or that boat noise simply may not represent an immediate threat to survival in this species. These findings contrast recent studies that have shown elevated stress responses in fishes when exposed to boat noise and highlights that inter-specific differences must be considered when evaluating potential impacts of anthropogenic noise on marine life.

Coral reef ecosystems are highly sensitive to microbial activities that result from dissolved organic matter (DOM) enrichment of their surrounding seawater. However, the response to particulate organic matter (POM) enrichment is less studied. In a microcosm experiment, we tested the response of bacterioplankton to a pulse of POM from the mass-spawning of Orbicella franksi coral off the Caribbean coast of Panama. Particulate organic carbon (POC), a proxy measurement for POM, increased by 40-fold in seawater samples collected during spawning; 68% degraded within 66 h. The elevation of multiple hydrolases presumably solubilized the spawn-derived POM into DOM. A carbon budget constructed for the 275 µM of degraded POC showed negligible change to the concentration of dissolved organic carbon (DOC), indicating that the DOM was readily utilized. Fourier transform ion cyclotron resonance mass spectrometry shows that the DOM pool became enriched with heteroatom-containing molecules, a trend that suggests microbial alteration of organic matter. Our sensitivity analysis demonstrates that bacterial carbon demand could have accounted for a large proportion of the POC degradation. Further, using bromodeoxyuridine immunocapture in combination with 454 pyrosequencing of the 16S ribosomal RNA gene, we surmise that actively growing bacterial groups were the primary degraders. We conclude that coral gametes are highly labile to bacteria and that such large capacity for bacterial degradation and alteration of organic matter has implications for coral reef health and coastal marine biogeochemistry.

Primary production due to photosynthesis results in daytime oxygen production across marine and freshwater ecosystems. However, a prevalent, globally-occurring nighttime spike in dissolved oxygen (DO) challenges our traditional assumption that oxygen production is limited to daylight hours, particularly in tropical coral reefs. When considered in the context of ecosystem oxygen budget estimates, these nocturnal spikes in DO could account for up to 24 percent of the daytime oxygen production. Here we show, 1) the widespread nature of this phenomenon, 2) the reproducibility across tropical marine ecosystems, 3) the lack of a consistent abiotic mechanism across all datasets we examined, and 4) the observation of nighttime DO spikes in vitro from incubations of coral reef benthic samples. Our study suggests that in addition to physical forcing, biological processes may be responsible for the production of oxygen at night, a finding that demands additional research.

Primary production due to photosynthesis results in daytime oxygen production across marine and freshwater ecosystems. However, a prevalent, globally-occurring nighttime spike in dissolved oxygen (DO) challenges our traditional assumption that oxygen production is limited to daylight hours, particularly in tropical coral reefs. When considered in the context of ecosystem oxygen budget estimates, these nocturnal spikes in DO could account for up to 24 percent of the daytime oxygen production. Here we show, 1) the widespread nature of this phenomenon, 2) the reproducibility across tropical marine ecosystems, 3) the lack of a consistent abiotic mechanism across all datasets we examined, and 4) the observation of nighttime DO spikes in vitro from incubations of coral reef benthic samples. Our study suggests that in addition to physical forcing, biological processes may be responsible for the production of oxygen at night, a finding that demands additional research.

Effective watershed management is crucial for mitigating soil erosion and ensuring sustainable land use management. This study prioritised watersheds in the Noun Division for erosion control by assessing morphometric and land use parameters. We employed a data-driven approach, integrating Geographic Information System and Remote Sensing techniques to delineate seven sub-watersheds, compute their morphometric, land cover attributes, and prioritise them for erosion management. Thirteen linear, five areal, and seven relief morphometric parameters were derived from terrain-corrected ALOS PALSAR DEM while five land use and land cover (LULC) classes were mapped out from quarterly mosaicked Sentinel-2 imagery. A compound ranking methodology was employed, guided by the assumption that linear and relief attributes positively correlate with erosion risk, while areal attributes correlate negatively. Hence, watersheds exhibiting low areal and high linear and relief morphometric values were assigned higher priority ranks. Similarly, watersheds predominantly characterised by settlements and agricultural land were ranked higher, whereas those dominated by forest, rangeland, and wetland were accorded lower ranks. The final prioritisation was based on the mean compound rank across the thirty parameters, with lower averages indicating higher susceptibility. The prioritisation results identified the Mvi watershed as the highest priority for erosion management, with a mean compound rank of 2.33, followed by the Bamendjin (3.50) and Nkoup (3.57) watersheds. Farmlands cover 62.02%, 52.19%, and 49.71% of the Mvi, Nkoup, and Bamendjin areas, respectively, implying that sustainable agricultural practices can play a pivotal role in mitigating erosion risks within these high-priority zones. The study recommends the implementation of soil-conserving agricultural practices like afforestation, cover cropping and minimum tillage in high-priority areas to mitigate erosion risk. It also advocates further research at the micro‑watershed scale within high‑priority zones that incorporates the impacts of LULC change to identify localised erosion hotspots for targeted management.

Primary production due to photosynthesis results in daytime oxygen production across marine and freshwater ecosystems. However, a prevalent, globally-occurring nighttime spike in dissolved oxygen (DO) challenges our traditional assumption that oxygen production is limited to daylight hours, particularly in tropical coral reefs. When considered in the context of ecosystem oxygen budget estimates, these nocturnal spikes in DO could account for up to 24 percent of the daytime oxygen production. Here we show, 1) the widespread nature of this phenomenon, 2) the reproducibility across tropical marine ecosystems, 3) the lack of a consistent abiotic mechanism across all datasets we examined, and 4) the observation of nighttime DO spikes in vitro from incubations of coral reef benthic samples. Our study suggests that in addition to physical forcing, biological processes may be responsible for the production of oxygen at night, a finding that demands additional research.