Posts Tagged 'annelids'

Influence of physico-chemical parameters and pCO2 concentration on mangroves-associated polychaetes at Pichavaram, southeast coast of India

Studies related to partial pressure of carbon dioxide (pCO2) concentration linking with polychaete diversity in mangrove ecosystems are limited in time and space. Therefore, the present study was conducted during July 2017–June 2018 on a monthly interval and reported the concentration of pCO2 coupled with physico-chemical parameters in relation to polychaetes diversity in Pichavaram mangroves ecosystem, southeast coast of India. Totally, 41 species were identified and the most dominant species were Prionospio cirrifera, P. cirrobranchiata, P. sexoculata, Prionospio sp. and Capitella capitata. Among the stations, higher polychaete diversity was found in marine zone compared to other zones. The correlation reflected a significant positive linear relationship between dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC) and CO2 versus pCO2. The carbon species DIC, DOC, POC and pCO2 concentration ranged from 1100.1 to 2053.3(µmol/kg), 165.7–1954.0(µmol/kg), 4.5–89.2(µmol/kg) and 184.7–3763.1(µatm), respectively. Further, the statistical analyses revealed that there was a strong correlation among carbon species with distribution of polychaete species in various zones of mangroves and thus indicating pivotal role in occurrence of polychaetes in mangroves.

Continue reading ‘Influence of physico-chemical parameters and pCO2 concentration on mangroves-associated polychaetes at Pichavaram, southeast coast of India’

Epibenthic community variation along an acidified tropical estuarine system

The benthic communities associated with hard substrata in tropical estuaries (rocky surfaces and mangrove roots) are underexplored compared to sediment-associated communities. Being unaffected by within-sediment chemistry, rocky surface communities are exposed to water-column chemistry. Natural and anthropogenic acidic inflows into estuaries are common, yet understanding of how low pH estuarine water impacts communities is limited. This study investigated variation in a rocky substratum benthic community along a steep pH and carbonate saturation gradient in a tropical estuary. Samples (n=72) samples were collected from four stations in the Brunei estuarine system, South East Asia (pH 5.78 – 8.1, salinity 0.1 – 29.5 psu). Species richness, diversity and abundance were greatest at the seaward end of the estuary (where pH and salinity were high), reduced in the middle estuary, and relatively high again in the upper estuary. A total of 34 species were recorded, with station abundances varying between 95 and 336 individuals/100 cm2. At a coarse taxonomic level (class/order), multivariate analyses revealed three distinct communities, a tanaid–polychaete dominated community, a mussel–dipteran community, and a mussel–amphipod–dipteran community. The observed shift from amphipod-dominance to polychaete-dominance along a decreasing pH gradient is consistent with the community changes seen in open ocean systems influenced by elevated pCO2. This study is the first description of community structure variation for hard-substratum invertebrates in an old-world tropical estuary. It shows that acidified estuaries offer insights into community-level responses to marine acidification in general.

Continue reading ‘Epibenthic community variation along an acidified tropical estuarine system’

Stress across life stages: impacts, responses and consequences for marine organisms

Highlights

• The published data were analysed to assess carry-over effects on marine organisms.

• The capacity of larvae to recover from early starvation and hypoxia was tested.

• Food limitation is the main driver of negative carry-over effects on juvenile growth.

• Larvae can recover from the early stress without negative imprints as juveniles.

• Carry-over effects depend on the duration of stress relative to larval period.

Abstract

Population dynamics of marine organisms are strongly driven by their survival in early life stages. As life stages are tightly linked, environmental stress experienced by organisms in the early life stage can worsen their performance in the subsequent life stage (i.e. carry-over effect). However, stressful events can be ephemeral and hence organisms may be able to counter the harmful effects of transient stress. Here, we analysed the published data to examine the relative strength of carry-over effects on the juvenile growth of marine organisms, caused by different stressors (hypoxia, salinity, starvation, ocean acidification and stress-induced delayed metamorphosis) experienced in their larval stage. Based on 31 relevant published studies, we revealed that food limitation had the greatest negative carry-over effect on juvenile growth. In the laboratory, we tested the effects of short-term early starvation and hypoxia on the larval growth and development of a model organism, polychaete Hydroides elegans, and assessed whether the larvae can accommodate the early stress to maintain their performance as juveniles (settlement and juvenile growth). Results showed that early starvation for 3 days (∼50% of normal larval period) retarded larval growth and development, leading to subsequent reduced settlement rate and juvenile growth. When the starvation period decreased to 1 day, however, the larvae could recover from early starvation through compensatory growth and performed normal as juveniles (c.f. control). Early exposure to hypoxia did not affect larval growth (body length) and juvenile growth (tube length), but caused malformation of larvae and reduced settlement rate. We conclude that the adverse effects of transient stress can be carried across life stages, but depend on the duration of stressful events relative to larval period. As carry-over effects are primarily driven by energy acquisition, how food availability varies over time and space is fundamental to the population dynamics of marine organisms.

Continue reading ‘Stress across life stages: impacts, responses and consequences for marine organisms’

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.’


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Ocean acidification in the IPCC AR5 WG II

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