Environmental Drivers of Macroinvertebrate Assemblages within Peat Pool Habitat-Implication for Bioassessment

Macroinvertebrates are a crucial component of wetland trophic webs. Many taxa are used as bioindicators of ecosystem change. However, relationships between macroinvertebrates and the environmental factors in peat pool habitats are still not well recognized. The present study shows the results of long-term studies during the years 2010–2020, on the responses of macroinvertebrates to the changes of environmental variables in a peat pool habitat formed as a result of peat exploitation on continental raised bog. The RDA analysis significantly explained 87.3% of the variance in macroinvertebrates abundances. Assemblages of most taxa (Anisoptera, Chironomidae, Ceratopogonidae, Coleoptera, Hydrachnidia and Tabanidae) showed a strong relationship with N-NO3 and pH. Moreover, densities of Chaoboridae larvae were explained by chlorophyll-a concentrations. Dominant taxon, Chironomidae, constituted from 48% to 87% of total faunal density. The highest proportions showed larvae of Psectrocladius sp. (gr. sordidellus) and Chironomus sp. Changes in the composition of macroinvertebrate fauna over a period of 10 years reflect the eutrophication process of the peat pool and deterioration of habitat conditions.

FORAMINIFERAL RECORD OF ENVIRONMENTAL CHANGES: PREEVAPORITIC DIATOMACEOUS SEDIMENTS FROM GAVDOS ISLAND, SOUTHERN GREECE.

The Messinian pre-evaporitic sedimentary succession of Gavdos island (Metochia section) is a nearly uninterrupted succession of marine sediments, dominated by finely laminated diatomaceous sediments, which are cyclically alternating with marlstone and white limestone beds. The purpose of this study is to analyze in detail the benthic and planktonic foraminiferal microfauna preserved in the sediments of this section. The qualitative and quantitative analysis of the planktonic foraminifera fauna allowed the recognition of seven bioevents, which have been astronomically dated for the Mediterranean. The base of the diatomitic succession in Gavdos Island is dated at 6.696 Myr, whereas its top at 6.0 Myr. Our results suggest that two environmental parameters are the most important factors that control the community structure of the benthic foraminiferal fauna: the food availability and oxygen concentration. In addition, local upwelling phenomena evidenced by signals from the benthic foraminifera and the distribution pattern of the planktonic G. bulloides may have played a role in the faunal density and composition

Benthic insects of the El Tala River (Catamarca, Argentina): longitudinal variation of their structure and the use of insects to assess water quality

The aim of this work was to determine the structure of the benthic entomofauna and its variation along the El Tala River (Catamarca, Argentina). Five sampling stations were established, considering the location of nearby housing with respect to the watercourse. The following variables were determined in situ: altitude, latitude and longitude, bedstream width, river depth, river-current speed, water and air temperatures. Benthic insects were collected with a square parcel sampler of 0.09-m2 area and 300-µm net opening and identified to the family level. Faunal density, richness, and diversity exhibited a longitudinal variation. From sampling Stations 1 (reference site) to 3, the number of orders and families decreased, whereas in sampling Station 4 those values increased and continued to do so through to Station 5 (downstream station). Station 5 showed the highest family richness (17) and the highest value for the Shannon-Wiener index (2.74) and the lowest value in Simpson's Dominance index (D = 0.22). These values could be explained because of the self-cleansing capabilities of the river downstream. The water quality of El Tala River is Class I (very clean and non-impacted), according to the results obtained from the application of the biotic Biological-Monitoring–Working-Party and Average-Store-per-Taxon indices.

Effects of mangrove removal on benthic communities and sediment characteristics at Mangawhai Harbour, northern New Zealand

Alfaro, A. C. 2010. Effects of mangrove removal on benthic communities and sediment characteristics at Mangawhai Harbour, northern New Zealand. – ICES Journal of Marine Science, 67: 1087–1104. The spread of mangroves at many locations in temperate northern New Zealand provides a stark contrast to the well-documented trend in mangrove forest decline recorded through the tropics and subtropics. To explore this difference, improved understanding is needed of New Zealand's mangrove ecosystems and how they respond to anthropogenic disturbance. The effect of mangrove removal on the community ecology of mangrove stands and adjacent habitats was investigated within Mangawhai Estuary, northern New Zealand, between March 2004 and September 2006. The vegetation, benthic macrofauna, and sediments were sampled within habitats (marshgrass, mangrove stands, pneumatophore zones, sandflats, and channels) at a treatment site (mangroves removed) and two undisturbed sites, before and after mangrove-removal activities. Mature mangrove habitats had less total abundance and fewer taxa than all the other habitats sampled and were dominated by pulmonate snails (Amphibola crenata) and mud crabs (Helice crassa). Whereas faunal composition varied seasonally as a result of life-history dynamics, temporal changes could be attributed to mangrove-removal activities. Mangrove eradication was followed by immediate changes in the sediment from a muddy to sandier environment, which favoured an overall increase in the abundance of crabs, snails, and bivalves. However, unexpected topographic catchment reconfigurations in late 2005 may have caused a subsequent increase in the delivery of silt and organic content to the study area and an overall decrease in faunal density in March and September 2006. The study provides direct evidence of the effect of mangroves on sediment and benthic faunal characteristics and the importance of catchment-derived imports to estuarine ecosystems.

Palaeoenvironment of Maastrichtian ostracods from ODP Holes 1049B, 1050C and 1052E in the Western North Atlantic

The Maastrichtian ostracods recovered from ODP Holes 1049B, 1050C and 1052E on the Blake Nose, Western North Atlantic, are investigated. The three sites are located on a depth transect encompassing middle to lower bathyal, Late Cretaceous palaeodepths. Fourteen samples ranging in age from early to late Maastrictian are investigated from Hole 1052E, which is the shallowest site. The early Maastrichtian G. falsostuarti–G. gansseri Zone of Hole 1052E yields rare ostracods. The species richness, abundance and faunal density are on average considerably higher in the late Maastrichtian R. fructicosa and A. mayaroensis Zones of Hole 1052E, possibly, at least partly, as a result of palaeoceanographical changes that were also responsible for the disappearance of the inoceramid bivalves at this location. A palaeobathymetrical comparsion among the late Maastrichtian ostracod assemblages recorded from Holes 1049B, 1050C and 1052E shows that the faunal density and mean number of taxa are inversely correlated with palaeodepth; however, the dominance of the platycopid genus Cytherella increases with palaeodepth. A dominance of platycopids may signify environmental stress related to low oxygen content. The dominance of the benthic foraminifer Nuttalides trumpeyi in the Late Cretaceous of Holes 1049B and 1050C provides additional evidence of oxygen deficiency. From a total of 28 genera recorded from Holes 1049B, 1050C and 1052E, 14 were previously recorded from Hole 689B, a high latitude hole in the Southern Ocean, and show that many ostracod genera display a wide latitudinal distribution in the Late Cretaceous deep sea, although more geographically restricted genera are also present, analogous with modern and Tertiary oceans.