Posts Tagged 'polychaetes'

Effects of estuarine acidification on an oyster-associated community in New South Wales, Australia

Many of the features that make estuaries among the most productive natural systems on earth also make them prone to acidification. Understanding the effects of estuarine acidification on different components of an ecological community is an important step in identifying indicators of ecosystem degradation. This study examined the impact of estuarine acidification, as a result of acid sulfate soil runoff, on wild Sydney rock oysters Saccostrea glomerata and their associated epifaunal communities in estuaries experiencing acid sulfate soil runoff in New South Wales, Australia. The responses of oysters and their invertebrate epifaunal communities to chronic acidification (greater than 6 mo; represented by oyster source site conditions) were assessed by examining the differences in oyster communities associated with moderate acidification (3.5 km from the source of acidification) or low acidification (8.2 km from the source). Oysters from moderate- or low-acidification sites were transplanted to a site with high exposure to acidification (less than 3 km from the source) or back to their original source sites (control) to mimic episodic acidification (2 wk). Epifaunal mussels Xenostrobus securis and limpets Patelloida mimula showed a negative association with oyster mortality, suggesting that these communities are closely tied to oyster survival. Oyster-associated epifaunal communities exposed to both chronic and episodic acidification were significantly different from communities with low exposure. Epifaunal communities exposed to episodic acidification were significantly less diverse than the control. Spionid and syllid worms were significantly less abundant and the mussel X. securis was significantly more abundant on oysters with moderate exposure or chronic exposure to acidification, as compared with communities from areas with low exposure to acidification. The mussel X. securis and the snail Bembicium auratum were significantly less abundant in oyster communities that were exposed to episodic acidification, as compared with the control. In systems where community composition depends on a single habitat-forming species, maintaining resistance may rely on the ability of that species to persist in the face of environmental stress.

Continue reading ‘Effects of estuarine acidification on an oyster-associated community in New South Wales, Australia’

Composition and spatial distribution of the meiofauna in the Wagner and Consag basins, Gulf of California, Mexico

In this study, we analyse the horizontal and vertical distribution of the meiofauna in the Wagner and Consag basins. Samples were collected at soft bottom sites on board of the R/V “El Puma” (WAGNER-02 Expedition) during July- August 2010 with a Smith McIntyre grab and 10 cm cores. At each station physical and chemical variables were measured including depth, salinity, pore water temperature and pH. Twelve higher taxa of meiofauna were recorded in both basins. Meiofauna was dominated by Nematoda (73.1%) followed by Copepoda Harpacticoida (11.28%), Polychaeta (8.41%) and Kinorhyncha (4.71%). Density of meiofauna in these two basins ranked from 19.12 to 742.20 ind.10 cm-2 and were mainly concentrated in the first four centimeters of the sediment (78.6%) and decreased with sediment depth; PERMANOVA analysis show significant differences among sediment depth layers. However, PERMANOVA analysis did not show significant differences of the abundances of meiofauna between basins. Multivariate Correspondence Canonica l Analysis (MCCA) was performed but the assemblages identified had no spatial gradient. This only confirms the patchy distribution already reported for the meiofauna. This analysis reported two faunal groups: Nematoda -Polychaeta and Copepoda – Kinorhyncha. In the present study, we report for the first time the horizontal and vertical distribution of the meiofauna in a natural CO2 venting area in the Gulf of California. There is still so much that we do not know about meiofauna processes, more studies are needed specially down to species level in order to have a clearer view of how environmental factors affect each species spatial distribution.

Continue reading ‘Composition and spatial distribution of the meiofauna in the Wagner and Consag basins, Gulf of California, Mexico’

Climate and environmental changes driving idiosyncratic shifts in the distribution of tropical and temperate worm reefs

An increasing number of studies have forecast the potential responses of marine life to future climate change. This study predicts how the distributional range of temperate and tropical worm reefs (WRs) might respond to climate and environmental changes (CECs). Compared with current distributions, the tested hypotheses were: (i) under a low CO2 concentration and active atmospheric carbon capturing scenario (RCP2.6), both tropical and temperate WRs will maintain their current distributions and face only slight multi-directional biogeographic changes along the century; and (ii) under a high CO2 concentration scenario (RCP8.5) WRs will shift toward higher latitudes, with marked changes for tropical species and slight changes for temperate species, specifically at the end of the 21st century. The hypotheses were tested using species distribution modelling, and exploratory statistical analyses were performed to tune model settings. Under scenario RCP2.6, in the middle of the century, areas of suitable habitat are predicted to slightly increase for the temperate WRs and conversely contract for tropical WRs. At the end of the century, multi-directional shifts without range retraction were predicted for both species, but tropical WRs showed major changes in their distribution. Under scenario RCP8.5 and throughout the century, multi-directional shifts increased the areas of suitable habitat for temperate WRs, whereas tropical WRs experienced shifts toward high latitudes and significant retraction at low latitudes. Results indicate that biogeographic range shifts are idiosyncratic for temperate and tropical WRs depending on the CECs scenarios considered.


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A comparison of life-history traits in calcifying Spirorbinae polychaetes living along natural pH gradients

Low-pH vent systems are ideal natural laboratories to study the consequences of long-term low-pH exposure on marine species and thus identify life-history traits associated with low-pH tolerance. This knowledge can help to inform predictions on which types of species may be less vulnerable in future ocean acidification (OA) scenarios. Accordingly, we investigated how traits of calcifying polychaete species (Serpulidae, Spirorbinae) varied with pH using a functional trait analysis at 2 natural pH gradients around the Castello Aragonese islet off Ischia, Italy. We first observed the distribution and abundance patterns of all calcifying polychaete epiphytes in the canopy of Posidonia oceanica seagrass across these gradients. We then used laboratory trials to compare fecundity, settlement success, and juvenile survival in the dominant species from a control (Pileolaria militaris Claparède, 1870) and a low-pH site (Simplaria sp.). We found significantly higher reproductive output, juvenile settlement rates, and juvenile survival in Simplaria sp. individuals from the low-pH site, compared to P. militaris individuals from control pH sites, when observed in their respective in situ pH conditions. Our results suggest that tolerance to low pH may result, in part, from traits associated with successful reproduction and rapid settlement under low-pH conditions. This finding implies that other species with similar life-history traits may respond similarly, and should be targeted for future OA tolerance research.

Continue reading ‘A comparison of life-history traits in calcifying Spirorbinae polychaetes living along natural pH gradients’

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Ocean acidification in the IPCC AR5 WG II

OUP book