Sponges

Suspension feeders perform a crucial role in uniting the benthic and pelagic environments in coral reef ecosystems. Of suspension feeders, sponges are one of the most highly abundant, widespread, and efficient filter-feeding organisms. However, suspension feeding in sponges is not completely understood. Previous studies have looked at the effect of temperature on pumping rate as well as the effect of particle size on retention rate. The purpose of this study was to investigate the depth-dependence of pumping rates and filtration efficiencies in two Caribbean reef sponges, Aplysina archeri and Aplysina lacunosa, at two depth profiles. Videos were taken of sponges pumping fluorescein dye to obtain pumping rates, and turbidity measurements were taken of both inhalant and exhalant water samples that were collected in situ via syringes in order to estimate filtration efficiency. The results revealed a species-specific interaction with depth for both pumping rate and filtration efficiency. Aplysina lacunosa was found to have both a faster pumping rate and increased filtration efficiency at the shallower depth, while no differences were observed across depths for A. archeri. Additionally, correlations were found between pumping rate and filtration efficiency for both species, suggesting the development of distinct filter-feeding strategies. Aplysina lacunosa had a positive correlation between pumping rate and filtration efficiency, while the correlation in A. archeri was found to be negative. Understanding the effect of depth on the filter-feeding mechanism of sponges is important to understanding the greater implications of the benthic-pelagic coupling process of sponges and suspension feeders in general.

This student research was retrieved from Physis: Journal of Marine Science XVI (Fall 2014)19: 6-12 from CIEE Bonaire.

Marine sponges provide an important link between the benthic and pelagic environments of coral reef ecosystems, yet there is relatively little known about them. Past studies have indicated that depth and size could be contributing factors in tube sponge filter feeding strategies. This study investigated the effects of depth and size on pumping rate and filtering efficiency of Aplysina lacunosa, a common Caribbean reef sponge. At two different depths, several parameters of the sponges were measured: tube length, wall thickness, tissue volume, pumping rate (using fluorescein dye), and filtering efficiency (percent reduction in turbidity between the ostia and osculum). Water samples collected from the water column had similar food availabilities between the two depths. There was a positive relationship between sponge size and pumping rate but not filtering efficiency. Additionally, no relationship was found between depth and sponge pumping rate and filtering efficiency, which is consistent with my finding that food availability did not differ across depths. The filter feeding strategy of A. lacunosa may be unique in the context of other benthic filter feeders in that its pumping rate but not filtering efficiency is affected by size and that neither pumping rate nor filtering efficiency are affected by depth. Further investigations are needed to learn more about the biology of A. lacunosa and its significance to Caribbean coral reefs.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 40-46 from CIEE Bonaire.

Stressors causing coral reef degradation are making reefs susceptible to domination by other organisms. One documented phase-shift is increased macroalgal cover of deteriorated reefs. Sponges also have the potential to overtake reefs because of their tolerance for rising temperatures and ocean acidification, ability to outcompete corals for space, and tendency to grow on available substrate created by coral mortality. This study aimed to address gaps in the literature on sponge/coral relationships as well as simultaneously study the interactions between coral and both of its potential competitors. Percentage encrusting sponge cover, percentage algae cover, and encrusting sponge density were compared to percentage live, damaged, and dead coral cover to examine the interactions among coral, sponges, and algae. Sponge/coral interactions were also classified to assess sponge aggressiveness. Data was collected at Yellow Submarine dive site using belt transects and photoquadrats. Although no correlations were significant, most comparisons found that sponges and algae decreased with more live coral cover and increased with more dead coral cover. No significant differences among the abundance of sponge/coral interaction types were found on the reef slope, but there were significant differences present on the reef crest. In both locations, most interactions were not aggressive overgrowth interactions. The relationships among sponges, algae, and coral suggest that both sponges and algae tend to grow on substrate made available by coral death. By examining the interactions of both sponges and algae with coral, comparison of these relationships was possible, potentially prompting future work that also assesses multiple ecologically important interactions.

This student research was retrieved from Physis: Journal of Marine Science XIX (Spring 2016)19: 42-51 from CIEE Bonaire.

Abtsract
This study describes in vivo cell turnover (the balance between cell proliferation and cell loss) in eight marine sponge species from tropical coral reef, mangrove and temperate Mediterranean reef ecosystems. Cell proliferation was determined through the incorporation of 5-bromo-2′-deoxyuridine (BrdU) and measuring the percentage of BrdU-positive cells after 6 h of continuous labeling (10 h for Chondrosia reniformis). Apoptosis was identified using an antibody against active caspase-3. Cell loss through shedding was studied quantitatively by collecting and weighing sponge-expelled detritus and qualitatively by light microscopy of sponge tissue and detritus. All species investigated displayed substantial cell proliferation, predominantly in the choanoderm, but also in the mesohyl. The majority of coral reef species (five) showed between 16.1±15.9% and 19.0±2.0% choanocyte proliferation (mean±SD) after 6 h and the Mediterranean species, C. reniformis, showed 16.6±3.2% after 10 h BrdU-labeling. Monanchora arbuscula showed lower choanocyte proliferation (8.1±3.7%), whereas the mangrove species Mycale microsigmatosa showed relatively higher levels of choanocyte proliferation (70.5±6.6%). Choanocyte proliferation in Haliclona vansoesti was variable (2.8–73.1%). Apoptosis was negligible and not the primary mechanism of cell loss involved in cell turnover. All species investigated produced significant amounts of detritus (2.5–18% detritus bodyweight−1·d−1) and cell shedding was observed in seven out of eight species. The amount of shed cells observed in histological sections may be related to differences in residence time of detritus within canals. Detritus production could not be directly linked to cell shedding due to the degraded nature of expelled cellular debris. We have demonstrated that under steady-state conditions, cell turnover through cell proliferation and cell shedding are common processes to maintain tissue homeostasis in a variety of sponge species from different ecosystems. Cell turnover is hypothesized to be the main underlying mechanism producing sponge-derived detritus, a major trophic resource transferred through sponges in benthic ecosystems, such as coral reefs.

Aim

Coral assemblages on Caribbean reefs have largely been considered to be biogeographically homogeneous at a regional scale. We reassess this in three taxa (corals, sponges and octocorals) using three community attributes with increasing levels of information (species richness, composition and relative abundance) across hierarchical spatial scales, and identify the key environmental drivers associated with this variation.

Location

Caribbean Basin.

Methods

We assessed reefs along 546 transects positioned within the same forereef habitat (Orbicella reef) in 11 countries, using a consistent methodology and surveyors. Spatial variability in richness, composition and relative abundance was assessed at four hierarchical spatial scales – transects (metres), sites (kilometres), areas (tens of kilometres) and regions (hundreds of kilometres) – using permutational multivariate analysis of variance (PERMANOVA). The relevance of contemporary environmental factors in explaining the observed spatial patterns was also assessed using PERMANOVA.

Results

Consistent with previous studies, species richness of coral assemblages, commonly the focus of biogeographical studies, showed little variance at large spatial scales. In contrast, species composition and relative abundance showed significant variability at regional scales. Coral, sponge and octocoral assemblages each varied independently across spatial scales. Rugosity and wave exposure were key drivers of the composition and relative abundance of coral and octocoral assemblages.

Main conclusions

Caribbean reef assemblages exhibit considerable biogeographical variability at broad spatial scales (hundreds of kilometres) when more responsive community attributes were used. However, the high degree of variability within sites (kilometres) highlights the relevance of local ecological drivers such as rugosity and wave exposure in structuring assemblages. The high levels of within-site variability that is not explained by environmental variables may suggest a previously unrealized contribution of anthropogenic disturbance operating at local scales throughout the region.

Sponges have a remarkable capacity to rapidly regenerate in response to wound infliction. In addition, sponges rapidly renew their filter systems (choanocytes)

to maintain a healthy population of cells. This study describes the cell kinetics
of choanocytes in the encrusting reef sponge Halisarca caerulea during early regeneration (0–8 h) following experimental wound infliction. Subsequently, we investigated the spatial relationship between regeneration and cell proliferation over a six-day period directly adjacent to the wound, 1 cm, and 3 cm from the wound. Cell proliferation was determined by the incorporation of 5-bromo-20-deoxyuridine (BrdU). We demonstrate that during early regeneration, the growth fraction of the choanocytes (i.e., the percentage of proliferative cells) adjacent to the wound is reduced (7.0 ± 2.5%) compared to steady-state, undamaged tissue (46.6 ± 2.6%), while the length of the cell cycle remained short (5.6 ± 3.4 h). The percentage

of proliferative choanocytes increased over time in all areas and after six days of regeneration choanocyte proliferation rates were comparable to steady-state tissue. Tissue areas farther from the wound had higher rates of choanocyte proliferation than areas closer to the wound, indicating that more resources are demanded from tissue in the immediate vicinity of the wound. There was no diVerence in the number of proliferative mesohyl cells in regenerative sponges compared to steady-state sponges. Our data suggest that the production of collagen-rich wound tissue is a key process in tissue regeneration for H. caerulea, and helps to rapidly occupy the bare substratum exposed by the wound. Regeneration and choanocyte renewal are competing and negatively correlated life-history traits, both essential to the survival of sponges. The eYcient allocation of limited resources to these life-history traits has enabled the ecological success and diversification of sponges. 

Four submersible dives off the coast of Bonaire (Caribbean Netherlands) and Klein Curaçao (Curaçao) to depths of 99.5–242 m, covering lower mesophotic and upper dysphotic zones, yielded 52 sponge specimens belonging to 31 species. Among these we identified 13 species as new to science. These are Plakinastrella stinapa n. sp., Pachastrella pacoi n. sp., Characella pachastrelloides n. sp., Geodia curacaoensis n. sp., Caminus carmabi n. sp., Discodermia adhaerens n. sp., Clathria (Microciona) acarnoides n. sp., Antho (Acarnia) pellita n. sp., Parahigginsia strongylifera n. sp., Calyx magnoculata n. sp., Neopetrosia dutchi n. sp., Neopetrosia ovata n. sp. and Neopetrosia eurystomata n. sp. We also report an euretid hexactinellid, which belongs to the rare genus Verrucocoeloidea, recently described (2014) as V. liberatorii Reiswig & Dohrmann. The remaining 18 already known species are all illustrated by photos of the habit, either in situ or ‘on deck’, but only briefly characterized in an annotated table to confirm their occurrence in the Southern Caribbean. The habitat investigated - steep limestone rocks, likely representing Pleistocene fossil reefs - is similar to deep-water fossil reefs at Barbados of which the sponges were sampled and studied by Van Soest and Stentoft (1988). A comparison is made between the two localities, showing a high degree of similarity in sponge composition: 53% of the present Bonaire-Klein Curaçao species were also retrieved at Barbados. At the level of higher taxa (genera, families) Bonaire-Klein Curaçao shared approximately 80% of its lower mesophotic and upper dysphotic sponge fauna with Barbados, despite a distance between them of 1000 km, indicating high faunal homogeneity. We also preliminarily compared the shallow-water (euphotic) sponge fauna of Curaçao with the combined data available for the Barbados, Bonaire and Klein Curaçao mesophotic and upper dysphotic sponges, which resulted in the conclusion that the two faunas show only little overlap

The Saba Bank is the largest submerged carbonate platform of 2,200 km2 in the Caribbean Sea, which lies partially within the Exclusive Economic Zone of the Netherlands and partially within the territorial waters of Saba and St. Eustatius. The Saba Bank houses an expansive coral reef ecosystem with a rich diversity of species and as such is also an important source of commercial fish for the nearby islands.

The Saba Bank furthermore forms the largest protected area of the Kingdom of the Netherlands, after the Dutch part of the Wadden Sea in Europe. It was declared a protected area by the Dutch Government in 2010 and has been registered as such in the Specially Protected Areas and Wildlife (SPAW) protocol of the Cartagena Convention for the Protection and Development of the Marine Environment of the Wider Caribbean. In 2012 it was internationally declared a Particularly Sensitive Sea Area (PSSA) by the International Maritime Organization (IMO) and an Ecological or Biological Significant Area (EBSA) by the Convention on Biological Diversity (CBD). As there are no large land masses nearby, the Saba Bank can be considered as relatively pristine and remote from human influences. Anthropogenic threats such as fisheries and environmental threats such as climate change, sea surface temperature increase and acidification, however, also threaten the Bank’s coral reefs.

As part of the Saba Bank research program 2011-2016, commissioned by the Dutch Ministry of Economic Affairs (EZ), expeditions to the Saba Bank were conducted in October 2011 and from 19 to 26 October 2013. The Saba Bank research program aims to obtain information on the biodiversity, ecological functioning and carrying capacity for commercial fisheries to facilitate sustainable management of the area. The expedition was funded by the Dutch Ministry of Economic Affairs and the World Wildlife Fund in the Netherlands.

The primary objectives of the 2011 and 2013 research expeditions were to collect data on benthic and reef fish communities, and on sponges and nutritional sources of the sponge community. Studies added to the 2013 expedition were research into the structural complexity of the reef; coral-algal interactions; and connectivity between populations. An international, multidisciplinary team of marine biologists investigated the coral reef structure as well as the spatial variation in species assemblages and population genetic connectivity of corals, algae, fish and sponges during eleven SCUBA dives at 20-30m depth.

During the expedition thirty-three 50m long transects resulted in more than 2000 images of the reef, and over 5000 fish counts of almost 100 fish species. A preliminary comparison with the data from 2011 gives the impression of a reduction in snappers, groupers and grunts, while there were noticeably more sharks. There were fewer algae on the Saba Bank than in 2011, possibly indicating a healthier reef, although there appeared to be a gradient of increasing algal cover towards the island of Saba. It seems unlikely that this is related to anthropogenic activities on the island, but more likely to natural causes.

An overview of collected data and preliminary results is given in this progress report. Further comparative analysis between the data collected in the 2011 and 2013 and further analysis between research components, e.g. between algal biomass, herbivorous fish biomass and nutrient levels, will be performed in 2014. This may give more information on the potential causes of the observed south-north algal gradient.

The expedition elicited large public interest and media coverage in both Dutch and Caribbean media (details provided in Appendix F). The work of the researchers, both above and under water, was also recorded on film as part of the documentary series Marine Life for Discovery Channel.

This month’s issue focuses attention on a very important species group – butterflies. Due to their sensitivity to environmental conditions, butterflies may serve as bioindicators for local and global environmental change. In addition to butterfly inventories and research across our islands, five years of butterfly monitoring on St. Eustatius is beginning to produce clear trends that indicate broader ecosystem change.

Also in this issue, on Saba the seafloor of the well-known site ‘The Pinnacles’ has been surveyed for the third time since 1991, resulting in the most detailed map of the seabed to date, demonstrating the benefit of improving technology for nature conservation(ists).

• ‘Research of the Month‘: Butterflies of the Windward Islands
• Butterflies as Beautiful Bio-indicators
• Butterfly Monitoring Programme on Statia
• Underwater Mapping on Saba
• Overview of Research and Monitoring Efforts
• Calendar of Upcoming Events, Meetings and Workshops

Abstract:

Sponges are major epibionts of mangrove roots in the Caribbean. Mangrove sponge communities in the Caribbean mainly consist of species that are typical to this habitat and community compositions often differ from those found on coral reefs nearby. Heterogeneity in species distributions between locations and within locations between roots is often reported. This study quantifies the diversity and abundance of mangrove associated sponges in the inner bays of Curaçao and Aruba and correlates variability of regional sponge diversity with environmental variables measured along the surveyed sites. Tannin concentrations vary between mangrove roots, and were correlated to sponge cover as a possible cause for habitat heterogeneity on a smaller scale. A total of 22 species was observed. Heterogeneity in species richness and abundance was apparent, and several sponge species were restricted in their depth of occurrence. Statistical data reduction suggests that sponge diversity may be partly explained by the distance towards adjacent reefs and to the degree of eutrophication, in which the latter is comprised of rate of planktonic respiration, total carbon and turbidity. Tannin concentrations did not determine within locality species heterogeneity as a priori postulated, but were positively related to sponge cover for reasons not yet elucidated.