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Anchialine pools are unique localized brackish water ecosystems, comprised of fresh groundwater and saltwater from the ocean mixing through subterranean pathways. This study characterized physicochemical properties, biological communities, and food web structures in anchialine pools on Hawaii Island, hypothesizing pronounced differences between pools with and without introduced fishes. Pools varied greatly in size, temperature, salinity, and dissolved oxygen saturation. On average, 46% of observed species were introduced. Native species of high conservation concern such as the shrimp Metabetaeus lohena and Halocaridina rubra were not observed in pools with introduced fishes, where periphytic algal biomass was lower. δC and δN analyses revealed an unusual food web structure where all animal species (except Gambusia affinis) occupied the same trophic niche, independent of species, size, and sex. These findings illustrate that simple food web structures with opportunistic feeding patterns in all species can occur in ecosystems that have greatly variable physicochemical properties and diverse biological communities. The wide variation in biological communities even in adjacent pools indicates that individual anchialine pools are unique. The high proportion of introduced species and their observed effects on these fragile ecosystems suggest that they pose a serious threat to native biota in Hawaiian anchialine pools. [ABSTRACT FROM AUTHOR]

Abstract: We present here a detailed case study on the lessons learned after a restoration process of a natural ecosystem, which can be considered as an ecological experiment. Senillar de Moraira is a brackish water small coastal lagoon located in the Spanish Mediterranean coast. It is separated from the sea by a sand bar and a beach, and is regularly fed by groundwater. Mostly due to the strong anthropogenic pressure this lagoon was degraded, and a restoration process, consisting mostly on the rebuilt of hydrogeomorphological features, was accomplished about a decade ago. After the restoration project, ecological monitoring was performed to reveal the recovery of the ecological integrity of the ecosystem, mainly focusing on the restoration of ecological processes and biological communities. Biological communities, rates of autotrophic (primary production) and heterotrophic (respiration) processes, sediment inputs and wash-out, and other ecological features were monitored during one and half year, two years after the restoration works finished, and the ecological patterns of the current functioning of this ecosystem were determined in order to suggest management strategies for its conservation. The maintenance of most anthropogenic pressures hardly allows the sustainability of natural processes to preserve the ecological health of the ecosystem. According to our results, the success of the restoration process is strongly compromised by the maintenance of most pressures, and subsidies are needed to allow the preservation of a somewhat natural condition of the ecosystem. Though many typical species and functional groups and processes re-established after the restoration, a progressive degradation was observed, especially reflected in the decline of submerged macrophytes that are essential to the maintenance of the ecological health of the system. The decline of these macrophytes was caused by a combination of impacts and risks that were not totally removed when restoration works were accomplished, namely the risk of occasional sewage inputs, increased salinity by groundwater overexploitation, enhanced siltation caused by deforestation in the catchment, and increased pressure of exotic species. This also resulted in a change of the functioning of the lagoon, from the dominance of autotrophic processes driven by macrophytes, to that of heterotrophic processes mediated by increased organic matter and inorganic nutrient inputs, and to the dominance of phytoplanktonic primary production, as revealed by the statistical analyses of the obtained data. This offers the lesson that attempts for ecological restoration without removing the causes of degradation result in the lack of self-sustainability of ecosystem functioning and drive to a perennial need for maintenance measures. [Copyright &y& Elsevier]

Abstract: The present study aims to detect functional diversity as well as functional redundancy patterns of soft bottom benthic communities in relation to the prevailing environmental factors, across several brackish water areas. We further tested whether differences in spatial scale can account for the possible variability in functional trait distribution, as well as for the local community assembly processes driven by species functional traits. Our main results suggested that environmental variation induces a large amount of variability in functional trait distribution at local and regional scale, a result which underscores the importance of habitat and environmental variation in the functioning of soft sediments in brackish areas. Conversely to functional diversity, functional redundancy remained invariable in both local and regional scales, therefore acting as an insurance against the enhanced environmental variability and maintaining ecosystem processes and services. Our findings led us also to conclude that environmental factors control the distribution of certain functional traits thus acting as environmental filters, in both local and regional scales. On the other hand, dominant species interactions accounted for the reduced levels of functional divergence at the less confined brackish water areas. This finding supported the view that interactions among dominant species can potentially induce negative effects on the functionality of brackish water soft sediments. From all the above, it is reasonable to assume that community shaping and functioning of the examined brackish water areas are governed by both biotic interactions and environmental filters, which are acting simultaneously at varying degrees of influence. [Copyright &y& Elsevier]

Abstract: In order to assess the suitability of Atyaephyra desmarestii as a bioindicator of the effects of hypoxic events on temperate freshwater systems, we investigated the respiratory responses of this shrimp to increasing temperatures and progressive hypoxia at two different salinities. This study, based on laboratory measurements, clearly demonstrates that this species has a moderate to poor oxygen regulatory ability and a high sensitivity to hypoxia. The respiratory response of the shrimp to increasing temperatures with increasing M O2 (low thermal regulation in oxygen uptake) was observed within a wide thermal range (15–30°C), although the species seems to be vulnerable to temperatures above 25°C in brackish water. This species copes best with hypoxia in brackish water but only at low to moderate temperatures (T ≤20°C). In freshwater, its habitual habitat, the ability of A. desmarestii to oxyregulate seems to be less temperature dependent. These features suggest that the respiratory response of A. desmarestii could be used in short-term stress bioassays to test the consequences of climate change and pollution events which lead to increased hypoxia of aquatic habitats. [Copyright &y& Elsevier]

Abstract: Alien species contribute to global change in all marine ecosystems. Environmental variability can affect species distribution and population sizes, and is therefore expected to influence alien species. In this study, we have investigated temporal variability of 11 alien species representing different trophic levels and ecological functions in two gulfs of the brackish Baltic Sea in relation to environmental change. Independent of the invasion time, organism group or the life-history stage, abundance and/or biomass of the investigated alien species was either stable or displayed abrupt increases over time. Timing in population shifts was species-specific and exhibited no generic patterns, indicating that the observed large shifts in environmental parameters have no uniform consequences to the alien biota. In general, the inter-annual dynamics of alien and native species was not largely different, though native species tended to exhibit more diverse variability patterns compared to the alien species. There were no key environmental factors that affected most of the alien species, instead, the effects varied among the studied gulfs and species. Non-indigenous species have caused prominent structural changes in invaded communities as a result of exponential increase in the most recent invasions, as well as increased densities of the already established alien species. [Copyright &y& Elsevier]

We examined the morphology of Skeletonema species occurring in coastal waters of southern Brazil, on the basis of LM, SEM, and TEM analyses of six isolated strains and of 13 field samples from the Patos Lagoon estuary and the adjacent Cassino Beach. We concluded that the genus Skeletonema is highly diverse in coastal waters of southern Brazil, with the occurrence of four confirmed species: S. costatum, S. pseudocostatum, S. potamos, and S. tropicum. In addition, EM details must still be provided for S. menzelii, and genetic studies should be conducted to confirm the identity of S. cf. grethae and S. subsalsum. The high diversity in this geographic area can be attributed to the proximity of the Subtropical Convergence and to the freshwater ecosystems of Patos Lagoon and La Plata River that favor the presence of warm-, cold-, and brackish-water species. [ABSTRACT FROM AUTHOR]

Shelled molluscs frequently exhibit a record of damage on exterior surfaces that can evidence past predation attempts and may affect survival and growth. In South Carolina populations of the ribbed marsh mussel, Geukensia demissa, >90% of the individuals and up to 60% of the total shell area are damaged. A trend toward greater amounts of damage occurred on mid-marsh compared to oyster reef mussels from the barrier beach side of inlets. Shell damage effects on survivorship and shell and tissue growth were assessed seasonally during multi- and single-season field experiments. Mussels from a common mid-marsh site were divided into size classes (~50 or 70 mm), treated to create two damage levels (undamaged and damaged), and replaced within mid-marsh exclusion cages to minimize additional shell damage. In both multi- and single-season experiments increased shell damage resulted in significantly greater mortality. Linear shell growth was unaffected by increased damage, but 50 mm mussels grew twice as fast. Shell mass increased 16–50% in the multi-season and single-season winter period, but decreased 7–12% during the single-season summer period. Tissue mass significantly decreased 31–43% in 50 mm damaged mussels, but increased by 33% for 70 mm mussels in both multi-season and the single-season winter period experiments. Shell damage did reduce tissue mass 43% in 70 mm single-season summer mussels. Experimental results indicate shell damage from a simulated increase in predation can affect negatively both survival and growth of marsh mussels. Seasonal timing of shell damage and initial mussel size also influenced the effects of sublethal predation on shell and tissue growth. The previously unrecognized importance of sublethal predation and the resultant significant negative effects of shell damage on survival and growth will affect the distribution and population dynamics of G. demissa in coastal marshes and will influence the overall contribution of ribbed mussels to estuarine ecosystems. [ABSTRACT FROM AUTHOR]

This study examines the distribution, composition, and structure of benthic communities in nine shallow-water semienclosed embayments on Cape Cod, southeastern Massachusetts. The spatial patterns were used to associate benthic characteristics with local environmental factors. Field data from multiple years were collected to measure macrofaunal abundance, community composition, and environmental characteristics. Multivariate statistics were used to analyze the spatial variations of species composition and the abundance of benthic macrofauna. Canonical ordination, specifically redundancy analysis, was used to determine the relative importance of the environmental factors (nutrients and habitat factors) being studied. The analyses demonstrate that the benthic communities in the shallow tidal embayments are clearly clustered in association with the local environments. Species composition and community structure of the benthic macrofauna are significantly correlated with water column parameters, especially with phytoplankton biomass, total nitrogen, and dissolved oxygen. [ABSTRACT FROM AUTHOR]

The macrofauna settling on experimental substrates was studied at two sites of the Lesina Lagoon to test its possible role in monitoring ecological variations in a brackish-water ecosystem. The community settlement was seasonally investigated on 3-month-old wooden poles; the development was monitored from 2001 to 2005. Comparisons with benthic assemblages settled on 10-yr-old poles were also performed. The main hydrological parameters were periodically measured during the study. A total of 38 species were collected. The assemblage reached the highest development in the central lagoon, showing relevant carbonate structures which supported a rich vagile fauna. Close to the sea-water inlet species richness and abundance values were lower, with the disappearance of some brackish-water species. A remarkable salinity drop during 2004 produced some faunistic changes in the assemblages, which however maintained different structures between the study sites, thus confirming macrozoobenthos as an efficient bioindicator of different environmental conditions for transition biotopes and a useful investigation tool in monitoring programmes. [ABSTRACT FROM AUTHOR]

In aquatic ecosystems, the ecology of macrophytal detritus aggregations has been investigated over a range of temporal scales. Yet, no attempts have been made to minimize the temporal resolution of the analysis, thus neglecting the occurrence of short-term colonization and decay dynamics for these ephemeral patches of high biological activity. The present study was carried out at two sampling sites in Lake Alimini Grande, a brackish lagoon in South-East Italy. The abundance of macroinvertebrate taxa colonizing prepared packs of reed leaf detritus and the ash-free dry mass of the packs were monitored daily for 40 days. Spectral analysis was used to investigate the fine-scale temporal dynamics of invertebrates colonization and leaf pack mass variations. The macrobenthos found on leaf packs was dominated at both sites by few taxa (i.e., the vagile Lekanesphaera monodi, Microdeutopus gryllotalpa, Neanthes caudata and the sessile Balanus sp.), whose general colonization patterns were described by unimodal curves. At a daily temporal resolution Balanus sp. was characterized by random short-term density variations, while vagile taxa showed non-random, highly site- and species-specific fluctuations generally characterized by an oscillation period comprised between 2 and 3 days. In addition, leaf packs were characterized by non-random, short-term mass oscillations, coherent and in phase with L. monodi abundance fluctuations. Our results highlight the occurrence of short-term, non-random density variations of invertebrate colonizers on leaf detritus patches. In addition, they emphasize a previously unexplored, fine-scale linkage between abundance patterns of invertebrate consumers and short-term mass variations of decaying detritus. [ABSTRACT FROM AUTHOR]