Posts Tagged 'BRcommunity'

Variability in sediment-water carbonate chemistry and bivalve abundance after bivalve settlement in Long Island Sound, Milford, Connecticut

Highlights

  • Total bivalve community composition influenced by grain size, pH, alkalinity, and date
  • Short term drivers of bivalve community settlement influenced by carbonate chemistry parameters
  • Different bivalve species respond to different carbonate chemistry cues for settlement.

Abstract

Cues that drive bivalve settlement and abundance in sediments are not well understood, but recent reports suggest that sediment carbonate chemistry may influence bivalve abundance. In 2013, we conducted field experiments to assess the relationship between porewater sediment carbonate chemistry (pH, alkalinity (At), dissolved inorganic carbon (DIC)), grain size, and bivalve abundance throughout the July–September settlement period at two sites in Long Island Sound (LIS), CT. Two dominate bivalves species were present during the study period Mya arenaria and Nucula spp. Akaike’s linear information criterion models, indicated 29% of the total community abundance was predicted by grain size, salinity, and pH. When using 2 weeks of data during the period of peak bivalve settlement, pH and phosphate concentrations accounted 44% of total bivalve community composition and 71% of Nucula spp. abundance with pH, phosphate, and silica. These results suggest that sediment carbonate chemistry may influence bivalve abundance in LIS.

Continue reading ‘Variability in sediment-water carbonate chemistry and bivalve abundance after bivalve settlement in Long Island Sound, Milford, Connecticut’

Impact of ocean acidification and warming on the diversity and the functioning of macroalgal communities (full thesis in French)

Predicted ocean acidification and warming for the end of the century may have drastic consequences on the structure and functioning of marine ecosystems. However, a lack of knowledge persists on the impact of future changes on the response of marine communities. This thesis aims to provide new understanding of the impact of ocean acidification and warming at the community level. For this, two ecosystems have been considered: rockpools, characterized by high physico-chemical variations, and maerl beds, with smaller variations. In the laboratory, artificial assemblages were created from the main calcareous and fleshy macroalgal and grazer species present in these two ecosystems. Created assemblages have been subjected to ambient and future temperature and pCO2 conditions. Ocean acidification and warming altered the structure and functioning of maerl bed assemblages, through an increase in the productivity of non-calcareous macroalgae and a decline in maërl calcification rates. The physiology of grazers is negatively impacted by future changes, which altered assemblages’ trophic structure. On the other hand, ocean acidification and warming had no effect on the productivity of rockpool assemblages. The highly variable environment may thus increase the resistance of rockpool communities to future changes, compared to communities from more stable environments, such as maerl beds.

Continue reading ‘Impact of ocean acidification and warming on the diversity and the functioning of macroalgal communities (full thesis in French)’

Short term CO2 enrichment increases carbon sequestration of air-exposed intertidal communities of a coastal lagoon

In situ production responses of air-exposed intertidal communities under CO2 enrichment are reported here for the first time. We assessed the short-term effects of CO2 on the light responses of the net community production (NCP) and community respiration (CR) of intertidal Z. noltei and unvegetated sediment communities of Ria Formosa lagoon, when exposed to air. NCP and CR were measured in situ in summer and winter, under present and CO2 enriched conditions using benthic chambers. Within chamber CO2 evolution measurements were carried out by a series of short-term incubations (30 min) using an infra-red gas analyser. Liner regression models fitted to the NCP-irradiance responses were used to estimate the seasonal budgets of air-exposed, intertidal production as determined by the daily and seasonal variation of incident photosynthetic active radiation. High CO2 resulted in higher CO2 sequestration by both communities in both summer and winter seasons. Lower respiration rates of both communities under high CO2 further contributed to a potential negative climate feedback, except in winter when the CR of sediment community was higher. The light compensation points (LCP) (light intensity where production equals respiration) of Z. noltei and sediment communities also decreased under CO2 enriched conditions in both seasons. The seasonal community production of Z. noltei was 115.54 ± 7.58 g C m−2 season−1 in summer and 29.45 ± 4.04 g C m−2 season−1 in winter and of unvegetated sediment was 91.28 ± 6.32 g C m−2 season−1 in summer and 25.83 ± 4.01 g C m−2 season−1 in winter under CO2 enriched conditions. Future CO2 conditions may increase air-exposed seagrass production by about 1.5-fold and unvegetated sediments by about 1.2-fold.

Continue reading ‘Short term CO2 enrichment increases carbon sequestration of air-exposed intertidal communities of a coastal lagoon’

Impact of carbonate saturation on large Caribbean benthic foraminifera assemblages

Increasing atmospheric carbon dioxide and its dissolution in seawater have reduced ocean pH and carbonate ion concentration with potential implications to calcifying organisms. To assess the response of Caribbean benthic foraminifera to low carbonate saturation conditions, we analyzed benthic foraminifera abundance and relative distribution in proximity to low carbonate saturation submarine springs and at adjacent control sites. Our results show that the total abundance of benthic foraminifera is significantly lower at the low pH low calcite saturation submarine springs than at control sites, despite higher concentrations of inorganic carbon at the spring sites. The relative abundance of symbiont-bearing foraminifera and agglutinated foraminifera was higher at the low pH low calcite saturation submarine springs compared to control sites. These differences indicate that non-symbiont bearing heterotrophic calcareous foraminifera are more sensitive to the effects of ocean acidification than non-calcifying and symbiont bearing foraminifera, suggesting that future ocean acidification may impact natural benthic foraminifera populations.

Continue reading ‘Impact of carbonate saturation on large Caribbean benthic foraminifera assemblages’

Coccolithophore community response along a natural CO2 gradient off Methana (SW Saronikos Gulf, Greece, NE Mediterranean)

A natural pH gradient caused by marine CO2 seeps off the Methana peninsula (Saronikos Gulf, eastern Peloponnese peninsula) was used as a natural laboratory to assess potential effects of ocean acidification on coccolithophores. Coccolithophore communities were therefore investigated in plankton samples collected during September 2011, September 2016 and March 2017. The recorded cell concentrations were up to ~50 x103 cells/l, with a high Shannon index of up to 2.8, along a pH gradient from 7.61 to 8.18, with values being occasionally <7. Numerous holococcolithophore species represented 60–90% of the surface water assemblages in most samples during September samplings. Emiliania huxleyi was present only in low relative abundances in September samples, but it dominated in March assemblages. Neither malformed nor corroded coccolithophores were documented. Changes in the community structure can possibly be related to increased temperatures, while the overall trend associates low pH values with high cell densities. Our preliminary results indicate that in long-termed acidified, warm and stratified conditions, the study of the total coccolithophore assemblage may prove useful to recognize the intercommunity variability, which favors the increment of lightly calcified species such as holococcolithophores.

Continue reading ‘Coccolithophore community response along a natural CO2 gradient off Methana (SW Saronikos Gulf, Greece, NE Mediterranean)’

Geographical CO2 sensitivity of phytoplankton correlates with ocean buffer capacity

Accumulation of anthropogenic CO2 is significantly altering ocean chemistry. A range of biological impacts resulting from this oceanic CO2 accumulation are emerging, however, the mechanisms responsible for observed differential susceptibility between organisms and across environmental settings remain obscure. A primary consequence of increased oceanic CO2 uptake is a decrease in the carbonate system buffer capacity, which characterizes the system’s chemical resilience to changes in CO2, generating the potential for enhanced variability in pCO2 and the concentration of carbonate [urn:x-wiley:13541013:media:gcb14324:gcb14324-math-0001], bicarbonate [urn:x-wiley:13541013:media:gcb14324:gcb14324-math-0002], and protons [H+] in the future ocean. We conducted a meta‐analysis of 17 shipboard manipulation experiments performed across three distinct geographical regions that encompassed a wide range of environmental conditions from European temperate seas to Arctic and Southern oceans. These data demonstrated a correlation between the magnitude of natural phytoplankton community biological responses to short‐term CO2 changes and variability in the local buffer capacity across ocean basin scales. Specifically, short‐term suppression of small phytoplankton (<10 μm) net growth rates were consistently observed under enhanced pCO2within experiments performed in regions with higher ambient buffer capacity. The results further highlight the relevance of phytoplankton cell size for the impacts of enhanced pCO2 in both the modern and future ocean. Specifically, cell size‐related acclimation and adaptation to regional environmental variability, as characterized by buffer capacity, likely influences interactions between primary producers and carbonate chemistry over a range of spatio‐temporal scales.

Continue reading ‘Geographical CO2 sensitivity of phytoplankton correlates with ocean buffer capacity’

Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming

Nitrogen fixation is a key source of nitrogen in the Baltic Sea which counteracts nitrogen loss processes in the deep anoxic basins. Laboratory and field studies have indicated that single-strain nitrogen-fixing (diazotrophic) cyanobacteria from the Baltic Sea are sensitive to ocean acidification and warming, 2 drivers of marked future change in the marine environment. Here, we enclosed a natural plankton community in 12 indoor mesocosms (volume ~1400 l) and manipulated partial pressure of carbon dioxide ( pCO2) in seawater to yield 6 CO2 treatments with 2 different temperature treatments (16.6°C and 22.4°C, pCO2 range = 360-2030 µatm). We followed the filamentous, heterocystous diazotrophic cyanobacteria community (Nostocales, primarily Nodularia spumigena) over 4 wk. Our results indicate that heterocystous diazotrophic cyanobacteria may become less competitive in natural plankton communities under ocean acidification. Elevated CO2 had a negative impact on Nodularia sp. biomass, which was exacerbated by warming. Our results imply that Nodularia sp. may contribute less to new nitrogen inputs in the Baltic Sea in the future.

Continue reading ‘Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming’


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Ocean acidification in the IPCC AR5 WG II

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