Posts Tagged 'Porifera'

Changes in the metabolic potential of the sponge microbiome under ocean acidification

Anthropogenic CO2 emissions are causing ocean acidification, which can affect the physiology of marine organisms. Here we assess the possible effects of ocean acidification on the metabolic potential of sponge symbionts, inferred by metagenomic analyses of the microbiomes of two sponge species sampled at a shallow volcanic CO2 seep and a nearby control reef. When comparing microbial functions between the seep and control sites, the microbiome of the sponge Stylissa flabelliformis (which is more abundant at the control site) exhibits at the seep reduced potential for uptake of exogenous carbohydrates and amino acids, and for degradation of host-derived creatine, creatinine and taurine. The microbiome of Coelocarteria singaporensis (which is more abundant at the seep) exhibits reduced potential for carbohydrate import at the seep, but greater capacity for archaeal carbon fixation via the 3-hydroxypropionate/4-hydroxybutyrate pathway, as well as archaeal and bacterial urea production and ammonia assimilation from arginine and creatine catabolism. Together these metabolic features might contribute to enhanced tolerance of the sponge symbionts, and possibly their host, to ocean acidification.

Continue reading ‘Changes in the metabolic potential of the sponge microbiome under ocean acidification’

So long and thanks for all the sponge: cryptic intertidal communities, consequences of ocean acidification, and new directions for science education

Ocean acidification (OA), defined as the reduction in the pH of global oceans, is predicted to have negative impacts on marine invertebrates. Within the past two decades there have been hundreds of studies on the effects of OA on the fitness, survival, and growth of many marine organisms, and yet there are several large gaps in our understanding. Many OA studies focus on one population (e.g. only sample from one site/location) of a widespread species and then make generalizations about that species as a whole. This is problematic for species that are spread between habitats with different levels of acidification. My work in Chapters 3 and 4 addresses the response of multiple populations of an important intertidal invertebrate to ocean acidification conditions on the Oregon coast; I describe the impacts of OA on the early life history (Chapter 3) and adult physiology (Chapter 4) of the common breadcrumb sponge Halichondria panicea. To investigate if H. panicea are adapted to local conditions, I utilized the persistent pattern of acidification that exists on the cape scale along the Oregon coast. I compared the responses of sponge populations that persist in areas of high, intermediate, and low acidification. I used both field and laboratory experiments to investigate the potential for local adaptation or acclimatization to OA conditions in H. panicea. In Chapter 3 I found that sponge larvae from areas that experience persistently high levels of ocean acidification may be less resilient to future levels of OA vs. larvae from other less acidified regions. Negative carryover effects for early exposure during brooding may result in increased larval mortality and faster rates of settlement; there were no effects of treatment on post-settlement processes for either population. Chapter 3 highlights a novel response of sponges to OA and reveals a potential population bottleneck during the critical larval stage for pre-exposed sponges under future OA conditions. Chapter 4 builds on the work of Chapter 3 by examining the response of adult sponges from high, middle, and low areas of OA along the Oregon coast. I used a common garden approach to untangle the effects of environmental acclimation and adaptation in a reciprocal transplant and mesocosm experiment. I observed changes in survival, mass, and Chlorophyll a (Chl- a) concentration. Consistent with Chapter 3, I found that prior exposure to OA resulted in increased mortality during the transplant and mesocosm experiment, although we found no evidence of treatment- or population-dependent effects on mass and chlorophyll a concentration in H. panicea populations. Combined, results of Chapters 3 and 4 suggests that sponges from highly acidified regions may be living near a threshold, past which the fitness of both larvae and adults would be compromised, with implications for the population as a whole.

Continue reading ‘So long and thanks for all the sponge: cryptic intertidal communities, consequences of ocean acidification, and new directions for science education’

Future ocean climate homogenizes communities across habitats through diversity loss and rise of generalist species

Predictions of the effects of global change on ecological communities are largely based on single habitats. Yet in nature, habitats are interconnected through the exchange of energy and organisms, and the responses of local communities may not extend to emerging community networks (i.e. metacommunities). Using large mesocosms and meiofauna communities as a model system, we investigated the interactive effects of ocean warming and acidification on the structure of marine metacommunities from three shallow‐water habitats: sandy soft‐bottoms, marine vegetation and rocky reef substrates. Primary producers and detritus – key food sources for meiofauna – increased in biomass under the combined effect of temperature and acidification. The enhanced bottom‐up forcing boosted nematode densities but impoverished the functional and trophic diversity of nematode metacommunities. The combined climate stressors further homogenized meiofauna communities across habitats. Under present‐day conditions metacommunities were structured by habitat type, but under future conditions they showed an unstructured random pattern with fast‐growing generalist species dominating the communities of all habitats. Homogenization was likely driven by local species extinctions, reducing interspecific competition that otherwise could have prevented single species from dominating multiple niches. Our findings reveal that climate change may simplify metacommunity structure and prompt biodiversity loss, which may affect the biological organization and resilience of marine communities.

Continue reading ‘Future ocean climate homogenizes communities across habitats through diversity loss and rise of generalist species’

Modelling the environmental niche space and distributions of cold-water corals and sponges in the Canadian northeast Pacific Ocean

Highlights

• We present the first comparison of realized niche space among six major, habitat-forming cold-water coral and sponge (CWCS) groups (sponge classes: Hexactinellida, Demospongiae; coral orders: Alcyonacea, Scleractinia, Antipatharia, Pennatulacea) occurring in the Northeast Pacific region of Canada (NEPC).
• The environmental gradients influencing CWCS niche space and breadth is driven by dissolved inorganic carbon, total alkalinity, and dissolved oxygen.
• Significant niche separation occurs among CWCS groups; high tolerance and marginality generally identify CWCS as specialists occurring in uncommon habitat conditions within the NEPC.
• Species distribution models developed for each CWCS group all share severely low dissolved oxygen ([O2] < 0.5 ml L−1) as a major predictor of habitat.
• Areas that are predicted to be suitable habitat for multiple CWCW groups primarily occurs primarily within 500–1400 m bottom depths on the continental slope and at offshore seamounts that have summits that reach into this depth range.

Abstract

Cold water coral and sponge communities (CWCS) are important indicators of vulnerable marine ecosystems (VMEs) and are used to delineate areas for marine conservation and fisheries management. Although the Northeast Pacific region of Canada (NEPC) is notable for having unique CWCS assemblages and is the location of >80% of Canadian seamounts, the extent of potential CWCS-defined VMEs in this region is unknown. Here, we used a diverse set of environmental data layers (n=30) representing a range of bathymetric derivatives, physicochemical variables, and water column properties to assess the primary factors influencing the niche separation and potential distributions of six habitat-forming groups of CWCS in the NEPC (sponge classes: Hexactinellida, Demospongiae; coral orders: Alcyonacea, Scleractinia, Antipatharia, Pennatulacea). The primary environmental gradients that influence niche separation among CWCS are driven by total alkalinity, dissolved inorganic carbon, and dissolved oxygen. Significant niche separation among groups indicates CWCS to be primarily specialists occurring in rare habitat conditions in the NEPC. Species distribution models (SDMs) developed for each CWCS group shared severely low dissolved oxygen levels ([O2] < 0.5 ml L−1) as a top predictor for habitat suitability in the NEPC. Niche separation is further emphasized by differences in the model-predicted areas of suitable habitat among CWCS groups. Although niches varied among taxa, the general areas of high habitat suitability for multiple CWCS groups in the NEPC occurred within the 500–1400 m bottom depth range which is strongly associated with the extensive oxygen minimum zone (OMZ) characterizing this region. As a result, the largest continuous area of potential CWCS habitat occurred along the continental slope with smaller, isolated patches also occurring at several offshore seamounts that have summits that extend into OMZ depths. Our results provide insight into the factors that influence the distributions of some of the most important habitat-forming taxa in the deep ocean and create an empirical foundation for supporting cold-water coral and sponge conservation in the NEPC.

Continue reading ‘Modelling the environmental niche space and distributions of cold-water corals and sponges in the Canadian northeast Pacific Ocean’

Sponge bioerosion versus aqueous pCO2: morphometric assessment of chips and etching fissures

Bioeroding sponges are important macroborers that chemically cut out substrate particles (chips) and mechanically remove them, thereby contributing to reef-associated sediment. These chemical and mechanical proportions vary with elevated levels of partial pressure of carbon dioxide (pCO2). To assess related impacts, the morphometric parameters “chip diameter” and “etching fissure width” were analyzed for Cliona orientalis Thiele, 1900, hypothesizing that their dimensions would differ with different pCO2 exposures (72 h at ca. 400, 750 and 1700 μatm). Under ambient conditions, we obtained a mean chip diameter of 21.6 ± 0.7 μm and a mean fissure width of 0.29 ± 0.01 μm. Chips were evenly distributed across the medium and coarse silt fractions regardless of treatment. We could not find a reliable pCO2 treatment effect for chip diameter and fissure width, but we observed strong data variability not related to our key questions. A hierarchical data design further reduced the test power. Fissure width was the more sensitive, but also more variable parameter. Sample size analyses nevertheless indicated that we had processed enough data. Thus, we reject our scenario of an increase in fissure width and consequent reduction in chip size to explain why chemical sponge bioerosion increases more strongly than the mechanical counterpart. Instead, we propose that a lowered ambient pH may favor respiratory acid build-up in the sponge tissue, possibly leading to a less localized bioerosion, causing bias towards more chemical bioerosion. Overall, this does not seem to affect the morphometry of sponge chips and the quality of sponge-generated sediment.

Continue reading ‘Sponge bioerosion versus aqueous pCO2: morphometric assessment of chips and etching fissures’

pH regulation and tissue coordination pathways promote calcium carbonate bioerosion by excavating sponges

Coral reefs are threatened by a multitude of environmental and biotic influences. Among these, excavating sponges raise particular concern since they bore into coral skeleton forming extensive cavities which lead to weakening and loss of reef structures. Sponge bioerosion is achieved by a combination of chemical dissolution and mechanical chip removal and ocean acidification has been shown to accelerate bioerosion rates. However, despite the ecological relevance of sponge bioerosion, the exact chemical conditions in which dissolution takes place and how chips are removed remain elusive. Using fluorescence microscopy, we show that intracellular pH is lower at etching sites compared to ambient seawater and the sponge’s tissue. This is realised through the extension of filopodia filled with low intracellular pH vesicles suggesting that protons are actively transported into this microenvironment to promote CaCO3 dissolution. Furthermore, fusiform myocyte-like cells forming reticulated pathways were localised at the interface between calcite and sponge. Such cells may be used by sponges to contract a conductive pathway to remove chips possibly instigated by excess Ca2+ at the boring site. The mechanism underlying CaCO3 dissolution by sponges provides new insight into how environmental conditions can enhance dissolution and improves predictions of future rates of coral dissolution due to sponge activity.

Continue reading ‘pH regulation and tissue coordination pathways promote calcium carbonate bioerosion by excavating sponges’

Sponges to be winners under near-future climate scenarios

Sponges are functionally important components of global benthic environments and have been proposed as potential winners under future climate scenarios. We review the evidence to support this hypothesis by examining the individual and combined effects of ocean warming (OW) and ocean acidification (OA) on sponges and comparing sponge responses with tolerance thresholds for other benthic organisms. Although sponges are generally tolerant of OA and may even benefit from elevated partial pressure of carbon dioxide, they are often sensitive to seawater temperatures only a few degrees higher than their normal range. Sponge responses to the combined effects of OA and OW are generally more positive than their response to OW alone. We found that sponges are generally less affected by OW or OA than are a number of currently dominant benthic organisms, such as corals. Therefore, sponges are expected to benefit under near-future climate scenarios, although species-specific differences in tolerance will likely shift the sponge assemblage composition toward more resilient species.

Continue reading ‘Sponges to be winners under near-future climate scenarios’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book