Posts Tagged 'annelids'

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’

Ocean acidification affects calcareous tube growth in adult stage and reared offspring of serpulid polychaetes

The energetically costly transition from free-swimming larvae to benthic life stage and maintenance of a calcareous structure can make calcifying marine invertebrates vulnerable to ocean acidification. The first goal of this study was to evaluate the impacts of ocean acidification on calcified tube growth for two Serpulidae polychaete worms. Spirorbis sp. and Spirobranchus triqueter were collected at 11 m depth from the Northwest Mediterranean Sea and maintained for 30 and 90 d, at three mean pHT levels (total scale) of 8.1 (ambient), 7.7, and 7.4. Moderately decreased tube elongation rates were observed in both species at a pHT of 7.7 while severe reductions occurred at pHT 7.4. There was visual evidence of dissolution and tubes were more fragile at lower pH but, fragility was not attributed to changes in fracture toughness. Instead, it appeared to be due to the presence of larger alveoli covered in a thinner calcareous layer. The second objective of the study was to test for effects in offspring development of the species S. triqueter. Spawning was induced, and offspring were reared in the same pH conditions the parents experienced. Trochophore size was reduced at the lowest pH level but settlement success was similar across pH conditions. Post-settlement tube growth was most affected. At 38 d post-settlement, juvenile tubes at pHT of 7.7 and 7.4 were half the size of those at pHT 8.1. Results suggest future carbonate chemistry will negatively affect initiation and persistence of both biofouling and epiphytic polychaete tube worms.

Continue reading ‘Ocean acidification affects calcareous tube growth in adult stage and reared offspring of serpulid polychaetes’

Ocean acidification buffers the physiological responses of the king ragworm Alitta virens to the common pollutant copper

Highlights

• Whilst ocean acidification (OA) often increases the toxicity of copper to marine invertebrates, here we find the opposite in the ragworm Alitta virens.

• There was no increase in copper-induced DNA damage or lipid peroxidation under OA conditions.

• Instead OA appeared to buffer the effects of copper on lipid peroxidation and acid-base disturbance, reducing these effects relative to ambient seawater conditions.

Abstract

Ocean acidification (OA) has the potential to alter the bioavailability of pH sensitive metals contaminating coastal sediments, particularly copper, by changing their speciation in seawater. Hence OA may drive increased toxicity of these metals to coastal biota. Here, we demonstrate complex interactions between OA and copper on the physiology and toxicity responses of the sediment dwelling polychaete Alitta virens. Worm coelomic fluid pCO2 was not increased by exposure to OA conditions (pHNBS 7.77, pCO2 530 μatm) for 14 days, suggesting either physiological or behavioural responses to control coelomic fluid pCO2. Exposure to 0.25 µM nominal copper caused a decrease in coelomic fluid pCO2 by 43.3% and bicarbonate ions by 44.6% but paradoxically this copper-induced effect was reduced under near-future OA conditions. Hence OA appeared to ‘buffer’ the copper-induced acid-base disturbance. DNA damage was significantly increased in worms exposed to copper under ambient pCO2 conditions, rising by 11.1% compared to the worms in the no copper control, but there was no effect of OA conditions on the level of DNA damage induced by copper when exposed in combination. These interactions differ from the increased copper toxicity under OA conditions reported for several other invertebrate species. Hence this new evidence adds to the developing paradigm that species’ physiology is key in determining the interactions of these two stressors rather than it purely being driven by the changes in metal chemistry under lower seawater pH.

Continue reading ‘Ocean acidification buffers the physiological responses of the king ragworm Alitta virens to the common pollutant copper’

Multiple stressor effects on macrobenthic communities in Corpus Christi Bay, Texas, U.S.A.

At any moment in nature, organisms are likely being exposed to multiple stressors, the effects of which are difficult to separate. Often, however, environmental stressors are considered on an individual basis. In southeastern Corpus Christi Bay, TX, declines in benthic macrofaunal community abundance, biomass, diversity, species richness, and species evenness have largely been attributed to the occurrence of hypoxia, a condition of low dissolved oxygen (DO). This study proposes that multiple stressors contribute to these observed benthic macrofaunal declines in southeastern Corpus Christi Bay. Therefore, a 30-year time series of water quality data (salinity, temperature, DO, pH, phosphate, ammonium, nitrite+nitrate, sulfate) and benthic community data (abundance, biomass, species richness, species evenness) was analyzed to describe 1) water quality dynamics of the region and 2) relationships between water quality dynamics and benthic macrofaunal response. Principal component analysis indicated that a large variability in the water quality dataset (63%) could be summarized by three principal components representing a multiple stressor index, a nutrient index, and an acidification index. Seasonality was found to be confounded with the multiple stressor index but not the nutrient or acidification indexes. Spearman rank-order correlations indicated both the multiple stressor and acidification indexes were inversely related to benthic macrofaunal community abundance, biomass, and species richness. A stepwise multiple linear regression analysis on individual water quality variables specified DO, and possibly temperature, to be leading explanatory variables for predicting benthic abundance. Temperature, pH, and nitrite+nitrate were indicated as leading explanatory variables for predicting benthic biomass. Temperature was indicated to be the only leading explanatory variable for predicting species richness. Results demonstrate that multiple stressors, including high temperature, high salinity, and low DO concentrations, are collectively acting on benthic communities in southeastern Corpus Christi Bay.

Continue reading ‘Multiple stressor effects on macrobenthic communities in Corpus Christi Bay, Texas, U.S.A.’

The influence of simulated global ocean acidification on the toxic effects of carbon nanoparticles on polychaetes

Highlights

• Slighter aggregation and more suspended carbon nanomaterials in acidified seawater

• Under pH acidified both carbon nanomaterials generated greater oxidative stress in polychaetes.

• Functionalized carbon nanomaterials increased oxidative stress and neurotoxicity under both pHs.

• Ocean acidification may cause a higher risk of carbon nanomaterials to marine ecosystems.

Abstract

Ocean acidification events are recognized as important drivers of change in biological systems. Particularlly, the impacts of estuarine acidification are severe than surface ocean due to its shallowness, low buffering capacity, low salinity and high organic matter from land drainage. Moreover, because they are transitional areas, estuaries can be seriously impacted by any number of anthropogenic activities and in the last decades, carbon nanomaterials (CNMs) are considered as emerging contaminants in the estuarine ecosystem. Considering all these evidences, chronic experiment was carried out trying to understand the possible alteration on the chemical behaviour of two different CNMs (functionalized and pristine) in predicted climate change scenarios and consequently, how these alterations could modify the sensitivity of one the most common marine and estuarine organisms (the polychaeta Hediste diversicolor) assessing a set of biomarkers related to polychaetes oxidative status as well as the metabolic performance and neurotoxicity. Our results demonstrated that all enzymes worked together to counteract seawater acidification and CNMs, however oxidative stress in the exposed polychaetes to both CNMs, especially under ocean acidification conditions was enhanced. In fact, although the antioxidant enzymes tried to cope as compensatory response of cellular defense systems against oxidative stress, the synergistic interactive effects of pH and functionalized CNMs indicated that acidified pH significantly increased the oxidative damage (in terms of lipid peroxidation) in the cotaminated organisms. Different responses were observed in organisms submitted to pristine CNMs under pH control, where the lipid peroxidation did not increase along with the increasing exposure concentrations. The present results further demonstrated the neurotoxicity caused by both CNMs, especially noticeable at acidified conditions. The mechanism of enhanced toxicity could be attributed to slighter aggregation and more suspended NMs in acidified seawater (demonstrated in the DLS analysis). Therefore, ocean acidification may cause a higher risk of CNMs to marine ecosystems.

Continue reading ‘The influence of simulated global ocean acidification on the toxic effects of carbon nanoparticles on polychaetes’

Effects of short-term and long-term exposure to ocean acidification on carbonic anhydrase activity and morphometric characteristics in the invasive polychaete Branchiomma boholense (Annelida: Sabellidae): a case-study from a CO2 vent system

Highlights
• Carbonic anhydrase activity remained unchanged after 30-days exposure to high pCO2.

• A significant decrease in weight was observed under short-term acclimatization to low pH.

• Enzyme activity and protein content showed a 50% increase under chronic exposure to OA.

• A significant variation in wet weight was detected under long-term exposure to low pH.

Abstract
The aim of this study was to test the effects of short- and long-term exposure to high pCO2 on the invasive polychaete Branchiomma boholense (Grube, 1878), (Sabellidae), through the implementation of a transplant experiment at the CO2 vents of the Castello Aragonese at the island of Ischia (Italy). Analysis of carbonic anhydrase (CA) activity, protein tissue content and morphometric characteristics were performed on transplanted individuals (short-term exposure) as well as on specimens resident to both normal and low pH/high pCO2 environments (long-term exposure). Results obtained on transplanted worms showed no significant differences in CA activity between individuals exposed to control and acidified conditions, while a decrease in weight was observed under short-term acclimatization to both control and low pH, although at low pH the decrease was more pronounced (∼20%). As regard individuals living under chronic exposure to high pCO2, the morphometric results revealed a significantly lower (70%) wet weight of specimens from the vents with respect to animals living in high pH/low pCO2 areas. Moreover, individuals living in the Castello vents showed doubled values of enzymatic activity and a significantly higher (50%) protein tissue content compared to specimens native from normal pH/low pCO2. The results of this study demonstrated that B. boholense is inclined to maintain a great homeostatic capacity when exposed to low pH, although likely at the energetic expense of other physiological processes such as growth, especially under chronic exposure to high pCO2.

Continue reading ‘Effects of short-term and long-term exposure to ocean acidification on carbonic anhydrase activity and morphometric characteristics in the invasive polychaete Branchiomma boholense (Annelida: Sabellidae): a case-study from a CO2 vent system’

Antioxidant efficiency of Platynereis spp. (Annelida, Nereididae) under different pH conditions at a vent’s system

Marine organisms are exposed to a pH decrease and to alteration of carbonate chemistry due to ocean acidification (OA) that can represent a source of oxidative stress which can significantly affect their antioxidant defence systems efficiency. The polychaetes Platynereis dumerilii and P. massiliensis (Nereididae) are key species of the benthic community to investigate the effect of OA due to their physiological and ecological characteristics that enable them to persist even in naturally acidified CO2 vent systems. Previous studies have documented the ability of these species to adapt to OA after short- and long-term translocation experiments, but no one has ever evaluated the basal antioxidant system efficiency comparing populations permanently living in habitat characterized by different pH conditions (acidified vs. control). Here, individuals of both Platynereis species, sampled from a natural CO2 vent system and from a nonventing “control” site in three different periods (April 2016, October 2016, and February 2017), were compared highlighting signals which suggested the ability of both species to acclimatize to high pCO2–low pH with slight seasonal variations of their antioxidant efficiency and the absence of disturbances of the oxidative status of Platynereis spp. tissues.

Continue reading ‘Antioxidant efficiency of Platynereis spp. (Annelida, Nereididae) under different pH conditions at a vent’s system’


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Ocean acidification in the IPCC AR5 WG II

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