Lagoon Ecosystem Research Articles

Late-Holocene paleoenvironmental history of bioluminescent Laguna Grande, Puerto Rico

Coastal lagoons are valuable natural resources and ecotourism hotspots that are at great risk due to human development and global climate change. In order to protect these resources it is important that we fully understand the paleoenvironmental history of these unique ecosystems and their sensitivity to environmental change. Here we present a multi-proxy (pollen, charcoal, grain-size, dinoflagellate cyst, stable isotope geochemistry, and foraminifera) 3600calyr B.P. record of paleoenvironmental change for Laguna Grande, Puerto Rico, which is a particularly unique coastal lagoon as it contains high abundances of the bioluminescent dinoflagellate Pyrodinium bahamense. Sedimentary evidence indicates that the Laguna Grande basin began accumulating sediment ~3600calyr B.P. coincident with regional sea level rise, but the modern lagoon itself is geologically quite young and did not become fully enclosed until ~575calyr B.P. due to longshore depositional processes and mangrove swamp development. Foraminifera assemblages suggest a potential breach of a protective barrier ~1550calyr B.P. perhaps as a result of a tropical storm or tsunami and is coincident with an increase in fire activity. Only two high-energy depositional units (tempestites) could be identified in the lagoon sediments over the last 575calyr B.P. indicating minimal impact by tropical storms or tsunamis on the lagoon since isolation from the open ocean. Fossil dinoflagellate cyst concentrations and influxes do not approach modern levels until ~200calyr B.P. and are currently at the highest levels in the history of the lagoon, indicating the lagoon may have become bioluminescent only recently, perhaps as a result of anthropogenic nutrient additions. Sedimentation rates support this hypothesis indicating a recent tripling of sedimentation rates when compared to millennial-scale sedimentation rates. This study highlights the utility of paleolimnological data in the management and preservation of at-risk coastal lagoon ecosystems.

Mercury in lagoons: An overview of the importance of the link between geochemistry and biology

Shallow-water lagoons, which are common features along coastlines, are important sites for elemental cycling in this environmentally-sensitive terrestrial–marine interface. Factors governing mercury (Hg) cycling in these lagoons are poorly characterized, but critical to understanding the links between sources and higher trophic levels, that are ultimately vectors of human exposure in lagoon environments. This article discusses the processes controlling the fate of Hg from various sources, including methylation of Hg, demethylation of methylmercury, and benthic fluxes of Hg species in three of the most thoroughly studied lagoons worldwide, namely Thau (France), Venice (Italy) and Marano and Grado (Italy). Although each lagoon system experiences differences in sources of Hg and details of how Hg is transformed and transported, Hg in each system is strongly affected by biogeochemical transformations of other elements, especially redox sensitive, microbially important elements such as sulphur, iron and manganese, and their interaction with organic matter. The shallow nature of lagoons and the rapid rates of microbially mediated organic matter decomposition result in seasonally dynamic processes that influence Hg bioavailability. Despite considerable work to date, the current understanding of Hg dynamics in lagoon ecosystems, through Hg distribution, MeHg production and degradation, and trophic transfer, is still limited and more research is needed to link all subparts into a general coherent picture.

Mercury in Different Feather Types from Great Cormorants (Phalacrocorax carbo L.) Inhabiting the Vistula Lagoon Ecosystem in Poland

Total mercury levels in different feather types (down, contour, tail and flight) in Great Cormorants (Phalacrocorax carbo L.) were determined using CV-AAS. Feathers from Great Cormorants inhabiting the Vistula Lagoon ecosystem have an average Hg level of 7.14 ± 3.99 (μg/g w.w.). Age-dependent concentrations of Hg were statistically significant (ANOVA Kruskal–Wallis, p < 0.0001). There were also significant differences in Hg levels in different parts of feathers from adults and immature birds (ANOVA Kruskal–Wallis, p < 0.0001). Cormorant chick feathers appear to be a potential biomonitor of Hg pollution in the Vistula Lagoon ecosystem, but this subject requires further research.

Exploring new issues for coastal lagoons monitoring and management

Coastal lagoons are productive and highly vulnerable ecosystems, but their management is still problematic mostly because they constitute transitional interface between terrestrial and marine domains. The “4th European Conference on Coastal Lagoon Research – Research and Management for the conservation of coastal lagoon ecosystems, South North comparisons”, was focused on the scientific research on coastal lagoons and the management for their conservation and sustainable use. Selected contributions were considered in this special issue of Estuarine Coastal and Shelf Science “Research and Management for the conservation of coastal lagoon ecosystems” as they deal with three important aspects for coastal lagoons management: (1) the design of monitoring programmes using biological compartments, (2) the ecosystem functioning and the impacts of perturbations and (3) ecosystem trajectories particularly after ecosystem restoration. Here we introduce the selected papers published in this issue, place these contributions in the perspective of the science-management interface and discuss new issues for coastal lagoon management.

MODIS-based sea surface temperature of the Baltic Sea Curonian Lagoon

This paper focuses on analysis of sea surface temperature (SST) derived from Terra/Aqua Moderate Imaging Spectrometer (MODIS) infrared imagery between 2000 and 2011 to document the hydrological regime in the Baltic Sea Curonian Lagoon. Records of the daytime SST from MODIS were validated against conventional in situ observations from an oceanographic buoy in the SE Baltic and two coastal hydrographic stations in the Curonian Lagoon. In general a very good agreement between them was found with positive bias (RMSD) not higher than 0.49°C (1.31°C) and R2 not less than 0.78. The MODIS-based SST data set, having a wide spatial coverage and relatively high spatial resolution enables one to study spatial, seasonal and inter-annual SST variations unavailable from sparse in situ measurements in the Curonian Lagoon. In addition satellite SST maps allow monitoring main spatio-temporal characteristics of mesoscale frontal features associated with the Curonian Lagoon coastal plume and coastal upwelling in the SE Baltic influencing coastal and lagoon ecosystems. The satellite infrared measurements and results obtained in near-shore waters in this study are unique and should be useful to researchers of near-shore water dynamics in other coastal regions of the world.

“You Can't Eat Money When You Are Hungry”: Campesinos, Manatee Hunting, and Environmental Regret in Veracruz, Mexico

AbstractSelf‐identified campesinos were interviewed in rural Veracruz, Mexico as part of this qualitative research study. Participants had firsthand historical knowledge about hunting the Antillean manatee (Trichechus manatus manatus) or about preparing the manatee for human consumption. The lagoon ecosystem that surrounds the area is greatly degraded and its contemporary inhabitants speak of the past with a great deal of wistfulness and a sense of loss characterized as “environmental regret.” The study examines the evolving local environmental and cultural practices, attitudes, and circumstances.

Herbicide-induced macrophyte-to-phytoplankton shifts in Japanese lagoons during the last 50 years: consequences for ecosystem services and fisheries

As expressed in the Ramsar Convention, the wise use of wetlands, including coastal lagoons, is one of the greatest environmental concerns across the globe. Seagrass beds are the key element for sustaining coastal lagoon ecosystems. Eutrophication, especially by nitrogen and phosphorus, has degraded many coastal waters and has been invoked as a major cause of seagrass disappearance worldwide. Seagrass had been used as fertilizer in Japan, and the removal of seagrass contributed to the decline of nutrients in the water. The shifts of primary producers from rooted macrophytes to phytoplankton occurred simultaneously between the mid-1950s and 1965 in Japan—presumably because of the wide use of herbicides for rice paddies. Increased phytoplankton induced the increase of fishery yield of clam on one hand and non-edible biofouling species on the other. Because a phytoplankton-dominated ecosystem is easily oxygen depleted at the bottom with the accumulation of organic matter of phytoplankton origin, preventing hypoxia is the key factor to maintain high secondary production for bivalve fisheries and sustainable use of the ecosystem of coastal lagoons.

Preface: Research and Management for the Conservation of Coastal Lagoon Ecosystems, South–North Comparisons

Coastal lagoons are aquatic ecosystems that share many features with estuaries, where seawater mixes with freshwater from continental origin, and also bear resemblances with shallow lakes as they often occur as shallow water bodies separated from the ocean by a barrier and are usually oriented parallel to the coastline (Kjerfve, 1994). The latter aspect may explain why in the vernacular languages of South France, Italy, and Spain the same word is used both for lagoons and for shallow lakes. On a global scale, these systems comprise 13% of world coastlines (Barnes, 1980) and 5.3% of the European coastlines. The SE coast of the Baltic Sea and the Atlantic and Mediterranean coasts of Southern Europe represent the major lagoon regions in Europe. The coastlines of the Mediterranean Sea comprise about six hundred lagoons that are listed by the Transitional Water Data Platform developed within the CIRCLEMED project ClimBioMedNet (www.circlemednet.unisalento.it). Some important hydrological, geomorphological, and biodiversity aspects of North African lagoons have been described in a special Hydrobiologia issue (Thomson & Flower, 2009). In the 1980s, the European research on coastal lagoons was focused on describing the geomorphology, hydrology, and ecological classification criteria, while during the 1990s it broadened in scope to include more functional ecology and biogeochemistry (Viaroli et al., 2005a). During the first decade of the 21st century, the coastal lagoon research has even further broadened in scope and now comprises a large panel of disciplines, including environmental economics, sociology, history, and politicology in addition to the natural sciences. The enforcement of the Water Framework Directive also stimulated a new effort in synthesizing knowledge and developing future research (Basset et al., 2005; Zaldivar et al., 2008; Tagliapietra et al., 2009). Some integrated projects have succeeded in developing successful interdisciplinary collaborations to tackle important questions about reconciling biodiversity conservation with human uses of lagoons, while placing the lagoons in the context of the aquatic Guest editors: R. de Wit, N. Mazouni & P. Viaroli / Research and Management for the Conservation of Coastal Lagoon Ecosystems: South – North Comparisons

Comparative bioaccumulation of trace metals using six filter feeder organisms in a coastal lagoon ecosystem (of the central-east Gulf of California)

The Tobari Lagoon, located in the central-east coast of the Gulf of California, receives effluents from the Yaqui Valley, one of the most extensive agricultural areas of México. The Tobari Lagoon also receives effluents from nearby shrimp farms and untreated municipal sewage. Surface sediment samples and six different species of filter feeders (Crassostrea corteziensis, Crassostrea gigas, Chione gnidia, Anadara tuberculosa, Chione fluctifraga, and Fistulobalanus dentivarians) were collected during the dry and the rainy seasons and analyzed to determine concentrations of cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn). Seasonal variations in metal concentrations in sediment were evident, especially for Cd, Cu, Hg, and Zn. The total and bioavailable concentrations of the five metals are not elevated in comparison to other areas around the world. The percentages of bioavailable respect to total concentrations of the metals varied from 0.6 % in Hg to 50.2 % for Cu. In the organisms, Hg showed the lowest concentrations (ranged from 0.22 to 0.65 μg/g) while Zn showed the highest (ranged from 36.6 to 1,702 μg/g). Linear correlations between the levels of Cu, Pb, and Zn in the soft tissues of C. fluctifraga and C. gnidia, and A. tuberculosa and C. gnidia were found. Seasonal and interspecies variations in the metal levels in filter feeders were found; F. dentivarians, C. corteziensis, and C. gigas exhibited the highest levels, could be used as biomonitors of metals contamination in this area.

Coastal lagoons and their evolution: A hydromorphological perspective

From a geoscience perspective, coastal lagoons are essentially ephemeral features which are part of a continuum of coastal environments. Their natural hydromorphological evolution is seldom if ever permitted to take place as a consequence of human action; either directly by engineering interventions, to maintain or create navigable inlets, or indirectly due to activities within their catchment areas. The hydromorphological impacts of historical, contemporary and proposed engineering activities in coastal lagoons around in the world are reviewed and from these a powerful exemplar is that of the Aveiro system in Portugal. Here, two centuries of channelization, jetty and breakwater construction and progressive dredging have transformed a then fluvially dominant system into one that is today tidally dominant. Both the tidal range and tidal prism have increased along with the extent of saline intrusion. The associated stresses imposed by increased tidal currents have, in turn, led to important changes in the sedimentary regime and to the loss of almost all seagrass species which were once abundant in the system. This, along with observations from other related case studies, raises important questions regarding the concept of lagoon ecosystem ‘health’ and the baseline or reference conditions to which it is assessed.

Origin and Distribution of Polycyclic Aromatic Hydrocarbons in Lagoon Ecosystems of Morocco

Polycyclic Aromatic Hydrocarbons (PAHs) were determined in sediments and bivalves by the Gas chromatography coupled to Mass spectrometer (GC/MS). PAHs concentrations in sediments of My Bousselham and Khnifiss, Atlantics lagoons, (expressed as ∑PAH) ranged from 31 to 82 ng/g of dry weight and from 6.6 to 34 ng/g of dry weight, respectively. Concerning organisms, PAHs levels contamination ranged from 28 to 117 ng/g of dry weight for My Bousselham (Ruditapes Decussates) and from 7 to 18.5 ng/g of dry weight for Khnifiss Lagoon Oyster (Crassostrea gigas). In the Med Lag (Nador), the results obtained showed a range varying from 6 to 126 ng/g of dry weight for sediments and from 24 to 32 ng/g of dry weight for organisms (Mytilus Galoprovincialis). The origin investigation of PAHs in sediment revealed, that the process of combustion was the main source in these Lagoons, while the diagenetic source, related to the high concentrations obtained of Perylene, was established only in both Atlantics Lagoons (Khnifiss and My Bousselham). A prevalence of high molecular weight PAHs was observed, with a considerable predominance of 4-ring PAHs in sediments and organisms of the My bousselham and Nador lagoons, while, no clear predominance was observed in the compartments studied in the Khnifiss lagoon. Correlation study of individual PAH between sediments and organisms, showed that absorption by Clams of low molecular weight PAH group, of which correlation was low, could be done through the water dissolved form, while the absorption of heavier molecular weight PAHs, which showed a high correlation of their distribution between sediments and Clams, could be the absorption from particulate matter.

Saprobity: a unified view of benthic succession models for coastal lagoons

We briefly review and expand upon classic conceptual models describing the succession of benthic communities along a gradient of organic matter (OM) enrichment developed for freshwater (the Saprobity System), coastal marine (the Pearson–Rosenberg [P–R] model) and lagoon (the Guelorget–Perthuisot [G–P] model) ecosystems. Differences and similarities between various approaches and models are highlighted and the P–R and G–P models are unified under a single conceptual framework of habitat saprobity in coastal lagoons. We refer to saprobity as the state of an aquatic ecosystem resulting from the input and decomposition of OM and the removal of its catabolites. In addition to other factors, such as salinity, saprobity is viewed as a selection factor for species diversity. The higher the saprobity is, the more impaired the system is, with progressively poorer benthic communities characterized by species that are increasingly tolerant of reducing conditions and toxicity. In coastal lagoons, these processes are strongly driven by hydrodynamics, which govern the land–sea gradient. Based on our review and analysis, we find that saprobity can be a useful descriptor of ecosystem state as determined by OM metabolism, suitable for characterizing the natural conditions of coastal lagoons and assessing their quality.

Historical flux of mercury associated with mining and industrial sources in the Marano and Grado Lagoon (northern Adriatic Sea)

The “MIRACLE” Project was established in order to assess the feasibility of clam farming and high levels of sediment mercury (Hg) contamination coexisting in the Marano and Grado Lagoon, Italy. This lagoon has been subjected to Hg input from both industrial waste (chlor-alkali plant) and long-term mining activity (Idrija mine, NW Slovenia). One of the subtasks of the “MIRACLE” Project was to determine the historical evolution of Hg accumulation in the lagoon’s bottom sediments. Thirteen 1-m deep sediment cores were collected from the subtidal and intertidal zones, plus one in a saltmarsh, all of which were then analyzed for total Hg content and several physicochemical parameters. Sedimentation rate assessments were performed by measuring short-lived radionuclides (excess 210Pb and 137Cs). For most of the analyzed cores, natural background levels of Hg were observed at depths of 50–100 cm. In the eastern area, Hg contamination was found to be at its maximum level at the core top (up to 12 μg g−1) as a consequence of the long-term mining activity. The vertical distribution of Hg was related to the influence of the single-point contamination sources, whereas the grain-size variability or organic matter content seemed not to affect it. In the western area, Hg content at the surface was found not to exceed 7 μg g−1 and contamination was recorded only in the first 20–30 cm. Geochronological measurements showed that the depositional flux of Hg was influenced by anthropogenic inputs after 1800, when mining activity was more intense. After 1950, Hg in the surface sediment, most remarkable in the central-western sector, seemed to also be affected by the discharge of the Aussa River, which delivers Hg from the chlor-alkali plant. In 1996, Hg mining at Idrija ceased, however the core profiles did not show any subsequent decreasing trend in terms of Hg flux, which implies the system retaining some “memory” of contamination. Thus, in the short term, a decrease in Hg inputs into the nearby Gulf of Trieste and the lagoon seems unlikely. A preliminary rounded-down gross estimate of total Hg “trapped” in the lagoon’s sediments amounted to 251 t. Such a quantity, along with the complexity of the lagoon ecosystem, suggests that an in toto reclamation of the sediments at the lagoon scale is unfeasible, both economically and environmentally.

Water Pollution by Surfactants: Fluctuations Due to Tourism Exploitation in a Lagoon Ecosystem

This paper describes recent levels of surfactants measured in a coastal lagoon ecosystem highly stressed by human activites: the Orbetello lagoon (Southern Tuscany, Italy, Ramsar Site IT008). Significance of difference among concentrations measured before and after summertime are explored in order to evaluate effects related to tourism exploitation. Among surfactants, methylene blue active anionic substances (MBAS) are selected as tracers for untreated discharges originated by domestic and urban activities. Water samplings were performed in 2011 following a randomly replicated nested logic model (n = 144). MBAS mean level of 0.070 mg.L–1 (–1) and 0.530 mg.L–1 (–1) are respectively recorded in June and October evidencing a significant increase after the touristic season. Possible MBAS concentration phenomena could be induced by different evaportaton rates among sampling stations and between winter and summer seasons and were evaluated, in this study, using water salinity as possible factor affecting samples segregations. Results evidence that differences of MBAS levels related to evaporation rates are trascurabile if compared to the variability induced by the presence of not-collected wastewater hot-spot pollution sources located closed around the urban settlement and along sandbars. Measured levels of surfactants could act negatively on living organisms both animals and plants contributing to affect Orbetello lagoon biodiversity. In this ecosystem, after the complete reorganization of urban wastewater treatment plants occured in 2008, further management actions should be focalized on reducing untreated sources of MBAS.

The use of cyprinodont fish, Aphanius fasciatus, as a sentinel organism to detect complex genotoxic mixtures in the coastal lagoon ecosystem

In the present work we aimed to standardise the alkaline comet assay with erythrocytes of the cyprinodont, Mediterranean Killifish, Aphanius fasciatus. The aims of the study were to explore the suitability of this fish to assess biomarkers of genotoxic effects and as a sentinel organism to detect complex genotoxic mixtures in coastal lagoon ecosystems. Following proper optimisation, the application and effectiveness of the comet assay in erythrocytes of A. fasciatus were tested by measuring the tail DNA (%) induced by (a) in vivo exposure of individual fish to X-rays (dose, 3 Gy) and (b) following in vitro challenge of erythrocytes with restriction endonucleases Fok-I and Eco-RI, which selectively induce double-strand breaks with cohesive and blunt termini, respectively. Furthermore, in order to evaluate whether circulating fish blood contained actively proliferating cells that could influence the extent of DNA damage in control (untreated) fish, we measured the number of “comets” positive for 5-bromo-2′-deoxyuridine (BrdU) by the use of anti-BrdU antibody and immuno-histochemical methods. Both treatments (i.e. with X-rays and restriction endonucleases) induced statistically significant increases in tail DNA (%) values compared with the relevant untreated controls, indicating the effectiveness of the comet assay in the erythrocytes of A. fasciatus to detect different types of DNA lesions. Results from anti-BrdU antibody labelling of erythrocytes indicated a very low percentage (5%) of “comets” positive for BrdU. Following optimisation and validation of the assay under laboratory conditions, fish were collected in the Orbetello lagoon (Tuscany, Italy), considered to be a significantly polluted site. The results showed statistically significant increases for tail DNA (%) compared with corresponding values observed in erythrocytes of fish caught in the unpolluted reference site “Saline di Tarquinia”. The effects of physico-chemical parameters of the water (i.e., salinity, pH and oxygen content) did not significantly influence the induction of DNA damage. These results indicate that the comet assay provides a reliable parameter and that A. fasciatus is a promising “sentinel organism” to detect the genotoxic impact of complex mixtures in coastal lagoon ecosystems.

Optimization of analytical procedures for the simultaneous voltammetric determination of total Hg(II) in presence of Cu(II) in environmental matrices

Abstract The present work reports the critical comparison about the employment of three different supporting electrolytes (0.1 mol L−1 HClO4, 0.01 mol L−1 EDTA-Na2 + 0.06 mol L−1 NaCl + 2.0 mol L−1 HClO4 and 0.1 mol L−1 KSCN + 0.001 mol L−1 HClO4) and their instrumental and chemical optimisation for the simultaneous voltammetric determination of total mercury(II) and copper(II) in sediments and sea water at gold electrode, especially discussing the reciprocal interference problems. The differential pulse anodic stripping voltammetric (DPASV) measurements were carried out using a conventional three-electrode cell: a gold electrode (GE) as working electrode, a platinum wire and an Ag‖AgCl‖KClsat as auxiliary and reference electrodes, respectively. The analytical procedure was verified by the analysis of standard reference materials: Estuarine Sediment BCR-CRM 277, River Sediment BCR-CRM 320 and Mercury in Water NIST-SRM 1641d. Once set up on the standard reference materials, the analytical procedure was transferred and applied to sediments and sea waters sampled in a lagoon ecosystem connected with Adriatic Sea (Ravenna area, Italy).

Vegetation cyclic shift in eutrophic lagoon. Assessment of dystrophic risk indices based on standing crop evaluations

Orbetello lagoon (Tuscany, Italy) is a meso-eutrophic, shallow-water ecosystem which has undergone cyclic shifts in macrophyte dominance since 1970. Field data on the total standing crops of Chlorophyceae and Rhodophyceae (from 1983 to 2011) and Angiospermae (seagrass; from 1998 to 2007), produced each year by the ecosystem, was acquired. A general lagoon environment quality score (decay level DL, categories 0–4) was attributed (a posteriori) for each annual dataset examined. Univariate and multivariate statistical analyses were used to relate total macrophyte standing crops of 29 years of monitoring to the general quality score. Two indices were proposed (Abundance of Macroalgae Index, AMI, and Abundance of Seagrass Index, ASI, the latter in two versions, ASI-1 and ASI-2) and tested against DL. The results showed that biomass data did not accurately describe general environmental quality of the lagoon ecosystem, whereas the indices gave a better fit. AMI showed the best performance, demonstrating that macroalga data was much more informative than seagrass data. Values of AMI over 4.0 were significantly associated with critical general quality scores (DL > 2).

Mapping Shallow Coastal Ecosystems: A Case Study of a Rhode Island Lagoon

In order to effectively study, manage, conserve, and sustain shallow-subtidal ecosystems, a spatial inventory of the basic resources and habitats is essential. Because of the complexities of shallow-subtidal substrates, benthic communities, geology, geomorphology, and water column attributes, few standard protocols are fully articulated and tested that describe the mapping and inventory processes and accompanying interpretations. In this paper, we describe a systematic approach to map Rhode Island's shallow-subtidal coastal lagoon ecosystems, by using, integrating, and reconciling multiple data sets to identify the geology, soils, biological communities, and environments that, collectively, define each shallow-subtidal habitat. We constructed maps for these lagoons via a deliberate, step by step approach. Acoustics and geostatistical modeling were used to create a bathymetric map. These data were analyzed to identify submerged landforms and geologic boundaries. Geologic interpretations were verified with video and grab samples. Soils were sampled, characterized, and mapped within the context of the landscape and geologic boundaries. Biological components and distributions were investigated using acoustics, grab samples, video, and sediment profile images. Data sets were cross-referenced and ground-truthed to test for inconsistencies. Maps and geospatial data, with Federal Geographic Data Committee (FGDC)-compliant metadata, were finalized after reconciling data set inconsistencies and made available on the Internet. These data allow for classification in the revised Coastal and Marine Ecological Classification Standard (CMECS). With these maps, we explored potential relationships among and between physical and biological parameters. In some cases, we discovered a clear match between habitat measures; in others, however, relationships were more difficult to distinguish and require further investigation.

Trematode communities in snails can indicate impact and recovery from hurricanes in a tropical coastal lagoon

In September 2002, Hurricane Isidore devastated the Yucatán Peninsula, Mexico. To understand its effects on the parasites of aquatic organisms, we analyzed long-term monthly population data of the horn snail Cerithidea pliculosa and its trematode communities in Celestún, Yucatán, Mexico before and after the hurricane (February 2001 to December 2009). Five trematode species occurred in the snail population: Mesostephanus appendiculatoides, Euhaplorchis californiensis, two species of the genus Renicola and one Heterophyidae gen. sp. Because these parasites use snails as first intermediate hosts, fishes as second intermediate hosts and birds as final hosts, their presence in snails depends on food webs. No snails were present at the sampled sites for 6 months after the hurricane. After snails recolonised the site, no trematodes were found in snails until 14 months after the hurricane. It took several years for snail and trematode populations to recover. Our results suggest that the increase in the occurrence of hurricanes predicted due to climate change can impact upon parasites with complex life cycles. However, both the snail populations and their parasite communities eventually reached numbers of individuals and species similar to those before the hurricane. Thus, the trematode parasites of snails can be useful indicators of coastal lagoon ecosystem degradation and recovery.

Linking classification boundaries to sources of natural variability in transitional waters: A case study of benthic macroinvertebrates

The assessment of human impacts on aquatic ecosystems requires separate quantification of natural and anthropogenic sources of environmental variability. This statement is very challenging in some categories of water bodies such as transitional waters, because they are naturally stressed ecosystems in which natural variability occur on different spatial scales (gradients versus patchiness) and temporal scales (regular versus pulse events). Among transitional water quality elements, benthic macroinvertebrates are the most exposed to natural variability patterns due to their life cycles and space-use behavior. In this article, we have evaluated the relevance of different potential sources of natural variability of benthic macroinvertebrate guilds on the temporal and spatial scales and we have quantified their effects on simple and multimetric descriptors of macroinvertebrate guilds; the latter included biomass and numerical densities, taxonomic diversity as well as M-AMBI and index of size spectra, ISS. The study was carried out using the TWReferenceNET database of 14 Eastern Mediterranean and Black Sea lagoons. Synoptic sampling of benthic macroinvertebrates was performed seasonally in different habitats within each lagoon in accordance with a nested design. All considered metrics showed a relatively high degree of variability among different reference stations and ecosystems, with the coefficient of variation ranging from 20% (log numerical density) to 45% (M-AMBI). The average values of every metric were significantly affected by the considered natural sources of variation: lagoon typology, seasonal period and habitat patchiness. Among components of lagoon typology, water salinity influenced the most the variation for both simple and multimetric descriptors. Seasonal period also had a strong influence, with higher values for all metrics before the summer season compared to the one after summer. Benthic habitat patchiness had a considerable influence only on the simple metrics, while continuous habitat variables significantly affected both M-AMBI and ISS. A general mixed model approach, used to quantify the relative influence of the different sources of variation on the considered metrics, allowed calculating type-specific boundaries for M-AMBI and ISS. The new boundaries significantly improved the accuracy of both multimetric indices in the classification of studied reference condition sites, with more than 75% of stations classified as good or high status. Nonetheless, results show that there is an intrinsic uncertainty in the classification of ecological status of lagoon ecosystem due to the degree of variability under reference conditions.