Euhaline Waters Research Articles

Assessment of a sheltered euhaline area of the southeastern Bay of Biscay to sustain bivalve production in terms of phytoplankton community composition

This study describes the phytoplankton community in sheltered euhaline waters of the Basque coast (southeastern Bay of Biscay). Phytoplankton composition, cell size, abundance, biomass and the presence of potentially toxic taxa, together with chlorophyll a, nutrients and hydrographic and optical conditions were measured, from August 2016 to August 2017, in the Mutriku port, with the main aim of assessing the suitability of the phytoplankton community as a food resource for bivalves. The water column in Mutriku showed the typical environmental conditions of Basque marine waters, with no significant nutrient enrichment caused by anthropogenic pressures. Haptophytes represented the greatest contribution to cell abundance (31–47%), and diatoms were the dominant group in terms of biomass (52–79%), which could favour mussel growth due to their high fatty acid content. In addition, the size structure of the phytoplankton community was suitable for mussel ingestion, since the predominant cell size was 2–20 µm. Regarding toxic phytoplankton, the genera that pose a risk for human health and those that affect negatively mussel physiology and survival were considered. Altogether, ten toxic phytoplankton taxa were identified, contributing in less than 5% to the total cell abundance of Mutriku. However, median chlorophyll a concentration was low (0.5 µg L−1), reflecting the oligotrophic conditions of the area. Therefore, even if the composition of the phytoplankton community could be favourable for bivalve aquaculture, biomass values are low compared to other zones of bivalve production.

Suitability of two areas of the Basque coast to sustain shellfish aquaculture according to both the presence of potentially toxic phytoplankton and the biotoxins regulated by the European Union

The composition and dynamics of microalgae play an important role in shellfish aquaculture, since phytoplankton is the main source of energy for filter-feeding bivalves as well as the main potential toxicity risk. Together with the increase in world aquaculture production in the last decades, there is recent interest in the implementation of shellfish aquaculture on the Basque coast (southeastern Bay of Biscay). In this context, the study of the potentially toxic phytoplankton abundance and dynamics has become essential, since the viability of shellfish aquaculture in the area could be compromised by biotoxins. In the present study, two euhaline sites of the Basque shelf, one inshore (Mutriku) and the other offshore (Mendexa), were compared during a one-year period. The main aim was to determine which site was more suitable for the development of shellfish aquaculture, from the perspective of exposure to toxic phytoplankton, by comparing the composition and abundance of the potentially toxic phytoplankton community and the concentrations of toxins in mussel flesh. The mussels that grew offshore presented a higher amount of okadaic acid (OA), in accordance with the fact that this site (Mendexa) also presented a higher cell abundance of Dinophysis acuminata, a potential producer of OA. In addition, although Dinophysis spp., Pseudo-nitzschia spp. and Alexandrium spp. exceeded their cell alert thresholds several times at both studied sites, the dinoflagellates presented a higher frequency of exceedance at Mendexa. Moreover, the percentage of samples with toxin concentrations that exceeded quantification limits was higher at Mendexa as well. Therefore, from the perspective of the currently regulated biotoxins, in the Basque Country, inshore euhaline waters seem to be more suitable for mussel aquaculture than offshore waters.

Dissolution rates of hydrated lime, Ca(OH) 2 in fresh, oligohaline, mesohaline and euhaline waters and its significance for liming of shrimp culture ponds

This study aimed at assessing the dissolution rates of hydrated lime, Ca(OH)2 in fresh, oligohaline, mesohaline and euhaline waters and discussing its significance for liming of shrimp culture ponds. Appropriate volumes of seawater and distilled water were mixed to prepare oligohaline (1–4 g/L) and mesohaline waters (4–15 g/L). One gram of analytical grade calcium carbonate, CaCO3, or one gram of analytical grade calcium hydroxide, Ca(OH)2, were applied in 10-L gallons filled with seawater (39.9 g/L), 10.7 g/L, 4.2 g/L and distilled water (0.0 g/L). The final TA of water was significantly higher for Ca(OH)2 than for CaCO3 only at salinities 4.2 and 10.7 g/L. It was concluded that hydrated lime, Ca(OH)2 is a better liming option than agricultural limestone, CaCO3 for moderately saline, hard and/or buffered waters (−4.5 ≤ Langelier saturation index, LSI ≤ −0.7). In poorly saline, hard and/or buffered waters (LSI < −4.5), limestone and lime would increase water TA similarly. Neither limestone nor lime should be applied on highly saline, hard and/or buffered waters (LSI > −0.7) because a TA decrease is expected.

Rating species sensitivity throughout gradient systems – a consistent approach for the Baltic Sea

Evaluating the state of benthic communities has played an important role in water quality assessments. Indices incorporating species sensitivities, richness and densities are commonly applied. In Europe, the importance of benthic indices has increased in the last years with the implementation of the European Marine Strategy Framework Directive (MSFD) which at the same time demands the applicability of an index across regional scales. To date, environmental variability is rarely considered in benthic indices and most sensitivity rankings have the disadvantages of static values (i.e. the same value in all areas), expert judgement and a limited geographical range.This study presents species sensitivity values calculated along environmental gradients for the Baltic Sea. Sensitivities were calculated according to the procedure of the Benthic Quality Index (BQI). We created a matrix of subregions, classes of salinity, depth and gear to identify comparable subsets for data analysis. Altogether, 19 subsets were defined within the Baltic Sea basins. Sensitivity values were calculated for 329 species out of a total of 678 species that were recorded in this study. Sensitivity values of taxa vary between subsets as it was expected for different environmental conditions. Most sensitivity values can be assigned to species occurring in euhaline and polyhaline waters. Distribution of species with high and low sensitivity values differed along the salinity gradient. In euhaline waters more species with high sensitivity values occurred than species with low sensitivity values, while in mesohaline waters the ratio of high and low sensitivity values among species was almost equal. In oligohaline waters more species with lower sensitivity values were present.For the first time, sensitivity values were calculated for a large number of species using the same method for the entire Baltic Sea. This results in a Baltic-wide comprehensive set of sensitivity values based on a dataset across subregional borders, and divided along environmental gradients and gear type. The same principles can be applied to transient waters from rivers to coastal lagoons as well as to other environments with gradients of, e.g. hydrodynamic characteristics. Publicly available sensitivity values will increase transparency and support the improvement of state assessments under the MSFD.

Bivalve pavements from shallow-water black-shales in the Early Jurassic of northern Italy: A record of salinity- and oxygen-depleted environmental dynamics

Thin shelled-bivalve pavements which constitute the Eomiodon horizon occur in a distinctive black-shale unit in the lowermost part of a Lower Jurassic carbonate platform sedimentary system, of the Southern Alps, Italy. The Eomiodon horizon is characterised by laminated mudstone and fissile, dark grey and black organic-rich marlstone and claystone, yielding abundant bivalve pavements with monotypic to paucispecific assemblages dominated by Eomiodon, an opportunistic, brackish, shallow-infaunal veneroid bivalve. Litho- and biofacies indicate environmental conditions ranging from nearshore euhaline waters to oxygen-depleted brackish lagoon, with a high input of terrestrial organic matter, culminating in marsh and terrestrial conditions. These pavements were analysed, using a microstratigraphic approach, while considering their taxonomic composition, the geometry of the beds, their biofabric criteria (size-sorting, abundance, fragmentation, orientation, and disarticulation), origin and time-averaging. These characteristics led to reconstruction of the following palaeoenvironmental dynamics:(1)the event concentrations, represented by mass mortality of stunted and juvenile individuals caused by anoxia, are indicative of deeper and predominantly stagnant parts of the lagoon;(2)an increase in shell sizes, higher growth rate and a decrease in size sorting and winnowing illustrate higher and more continuous bottom oxygenation and enhanced life in oxygen-fluctuated environmental conditions;(3)poorly sorted, highly fragmented and bioturbated bivalve accumulations indicate the Eomiodon habitat. Here, large-sized Eomiodon specimens record a decrease in water depth and sedimentation rate and almost constantly oxygenated bottom conditions;(4)the appearance of byssally attached bivalves (Lithioperna) marks the transition from the muddy–soupy substrate of the Eomiodon habitat to firm/hard bottom conditions. This new substrate allowed the settlement of Lithioperna, a byssate isognomonid, which records a shallower and landward marsh setting.The Eomiodon horizon testifies to a short-term warm–humid climatic phase and yielded Lithioperna, the first genus of the Lower Jurassic Lithiotis fauna to appear in Southern Alps. This fauna is composed of large and aberrant bivalves which are spread throughout the Lower Jurassic Tethyan and tropical Panthalassian carbonate platforms. As a result, the Eomiodon horizon and its salinity- and oxygen-depleted environmental setting represent a possible progenitor incubator for the Lithiotis fauna.

Scale-dependent movements and protection of female blue crabs (Callinectes sapidus)

Little is known about the migration of female crabs (Callinectes sapidus) to spawning grounds, or how effectively they are protected by North Carolina's “spawning sanctuaries.” To investigate migration, we tagged and released a total of 2700 mature female crabs in the fall of 2001 and the summer and fall of 2002 in the three tributaries of Pamlico Sound. Tag returns indicate that females begin migration during September to November and that they probably do not complete it until the next spring. To assess site fidelity and protection of females by spawning sanctuaries, 398 tagged adult females were released in or near sanctuaries at Ocracoke and Hatteras inlets. Most recaptures occurred near the barrier islands (Outer Banks), suggesting that mobility declines once females reach euhaline waters, but recapture data also showed that crabs move over scales larger than sanctuaries and derive only temporary protection by entering sanctuaries. Ovigerous females fitted with ultrasonic pingers were tracked after release inside the boundary of Ocracoke spawning sanctuary. Crabs with orange (new) egg masses meandered over small areas, but those with eggs approaching hatching moved directly seaward. Apparently spawning sanctuaries must be large to be effective; where this is not practical (as in North Carolina), other strategies should be considered.

Palaeoenvironments and palaeoclimates of the Quaternary molluscan faunas from the coastal area of Bahía Vera-Camarones (Chubut, Patagonia)

Quaternary molluscs are useful tools as indicators of environmental and climatic changes through time. The Patagonian coastal area exhibits a series of Quaternary marine terraces (MT) at various elevations with a well-preserved molluscan fauna. The assemblages from Mid– to Late Pleistocene and Holocene raised beach deposits exposed between Bahía Vera and Bahía Camarones (44.2°S–45°S) were examined, and systematic, palaeoecological and palaeobiogeographical aspects were reviewed and updated in terms of interpretation of the littoral area and biotic responses to climate changes. Collections at 10 fossiliferous localities and four modern sites of the adjacent nearshore show that molluscs (41 taxa: 24 gastropods and 17 bivalves) represent 91% of the total faunal content. Identification of the typical taxa for at least four sea-level highstands was based on the occurrence, relative abundance, species richness, and diversity indices (Margaleff's; Sannon Weaver's). Variations between terraces MTIII (Camarones, higher than + 30 m, probably ca. 400 ka), IV (Punta Pescadero and Camarones,+ 22–29 m, 178–239 ka), V (Bahía Vera, Punta Pescadero, Camarones,+ 16–18 m, 92–135 ka) and VI (Punta Lobería, Punta Pescadero, Camarones,+ 6–12 m, 2.5–8 ka) add to a better understanding of palaeoenvironments and palaeoclimates linked to sea-level highstands since MOIS11. Their original habitat was typical of rocky-shore, high-energy and euhaline waters, similar to the modern conditions of adjacent benthic communities. The most characteristic taxa are: Patinigera deaurata (Gm.), Fissurella spp., Crepidula protea d'Orb., C. aculeata (Gm.), C. cf. unguiformis Lam., Natica isabelleana d'Orb., Trochita pileus (Lam.), Buccinanops spp., Pareuthria plumbea (Philippi), Acanthina monodon (Pallas) and Trophon spp. (Gastropoda); Brachidontes purpuratus (Lam.), Protothaca antiqua (King), Clausinella gayi (Hupé), Mactra aff. patagonica (d'Orb.) and Ostrea tehuelcha (Feruglio). New records in this area for the Late Pleistocene are: C. aculeata (Gm.), C. onyx Sow., C. protea d'Orb., T. patagonica (d'Orb.), N. isabelleana (d'Orb.), B. rodriguezi (d'Orb.), A. tehuelchus (d'Orb.) and C. gayi (Hupé). Ostrea tehuelcha d'Orb. became extinct and Tegula atra (Lesson), N. isabelleana (d'Orb.), B. rodriguezi (d'Orb.), C. patagonica (d'Orb.) and D. vilardeboana (d'Orb.) migrated into the area. Exclusive for MTIII (MOIS11) are Pectinidae indet., Ostrea tehuelcha and Mactra cf. patagonica d'Orb. which, together with other taxa (i.e., Corbula patagonica, Diplodonta vilardeboana), suggest warmer sea surface temperature (SST) than at present. Typical of MTIV (MOIS7) are T. atra, biggest P. antiqua (King), and Veneroida indet. The assemblage from MTV (MOIS5c?, 5a?), T. atra, T. patagonica, C. dilatata Lamk., M. edulis Linn., B. purpuratus, P. antiqua, and P. rostratus (Koch), is not indicative of a climatic optimum and thus of the Last Interglacial maximum highstand (MOIS5e). MTVI (MOIS1) is characterized by B. cf. purpuratus, N. (Patinigera) magellanica (Gm.), N. (P.) deaurata (Gm.), Trophon geversianus (Pallas), B. purpuratus, and Aulacomya atra (Molina). N. delicatissima (Strebel), Chlamys sp., Panopea abbreviata, and Lyonsia sp. exclusively occur in the modern nearshore. According to the global isotope curve, MOIS5e highstand (125 ka BP) was the warmest since the Mid-Pleistocene. The innermost MTIII assemblage provides an opportunity to hypothesize that along the eastern coast of South America the corresponding highstand (probably MOIS11, ca. 400 ka BP ?) belongs to the warmest of the Pleistocene interglacials preserved, as proposed earlier for the Chilean coast (Ortlieb et al., 1996). This assemblage could be correlated with the Belgranense of the Bonaerensian littoral. The Holocene Climatic Optimum (5–8 ka) is confirmed to have influenced the littoral biota. A slightly higher SST (1–3 °C) implied atmospheric and palaeoceanographic changes, with a southwards shift of the dominant warm (Brazilian) and cool (Malvinas = Falkland) currents along the SWAtlantic and, consequently, of the Argentinean and Magellanean marine zoogeographical provinces.

Growth, feeding and distribution of the solenette Buglossidium luteum with particular reference to its habitat preference

Growth, condition, diet and spatial distribution of the solenette Buglossidium luteum (Risso, 1810) were investigated along the coasts of the French Atlantic, eastern English Channel and Southern Bight of the North Sea. Distribution and habitat preferences of solenette were analysed in relation to physical and biological features presumed to influence fish distribution. B. luteum was patchily distributed and concentrated in shallow muddy and muddy-sand bottoms moderately influenced by estuarine waters (euhaline waters). In the studied area, solenette seemed to find habitats suitable for growth. Food availability was not assumed to be a limiting factor for solenette distribution in contrast to abiotic factors such as salinity.

Age- and Sex-Dependent Migrations of Striped Bass in the Hudson River as Determined by Chemical Microanalysis of Otoliths

Patterns of habitat utilization and migration of Hudson River striped bass,Morone saxatilis, were estimated using otolith microchemical analysis to chart age- and sex-dependent movements. Otoliths from 25 males and 25 females were analyzed for seasonal and age-specific patterns in strontium: calcium level. These levels were converted into salinity estimates based upon a relationship derived from experimental studies. Seasonal patterns in salinity habitation indicated annual up-estuary migrations in mature age-classes of males and females, and may represent spawning migrations. Early emigration of young striped bass (<3 yr old) into polyhaline and euhaline waters was observed for both sexes, but females tended to reside at higher salinities throughout their life span. Otolith microchemical analysis indicated that 68% of the sampled females and 28% of the sampled males spent significant portions of their lives in euhaline coastal waters. A positive relationship between down-estuary movements and age was observed for both sexes, supporting the hypothesis of size-related dispersion and anadromy in striped bass populations. Individuals collected during the same season or from the same segment of the river had similar lifetime salinities. This result suggests that group cohesion (schooling) could persist for substantial periods of an individual’s life span. The most cohesive group was fall-collected males, which may reside permanently in fresh water and estuarine waters. Cohesive migratory groups would have important implications for investigations on effects of contaminants and fishing pressure on Hudson River striped bass.

Nutrient-rich saltwater and its influence on the phytoplankton of the patos lagoon estuary, Southern Brazil

Five cruises carried out in the main navigation channel of the Patos Lagoon estuary, southern Brazil, between June and December 1989, showed high concentrations of ammonium (up to 3.0 μM), nitrate (up to 13.0 μM), and phosphate (up to 3.0 μM) in the surface saltwater close to the lagoon's mouth. High values of chlorophyll a were also measured in euhaline waters. The influence of nutrient-rich saltwater on phytoplankton production was found in a sequence of weekly measurements conducted at a shallow fixed station between September and November 1989. Peaks of carbon uptake coincided with high nitrate concentration measured during the intrusion of saltwater. Possible causes for the positive relationship between salinity and nutrients such as sewage input, sediment resuspension and return of previously exported estuarine water to the lagoon are discussed.

Distribution and status of submerged vegetation in estuaries of the upper texas coast

Composition and biomass of beds of submerged aquatic vegetation (SAV) in estuaries along the upper Texas coast were examined from bottom core and rake samples taken along 72 line transects during July–August 1987. Substrate composition, salinity, water depth, and water clarity were also measured at each sample station.Halodule wrightii was the dominant species of SAV meadows (69% occurrence), followed byRuppia maritima (36%).Najas guadalupensis andVallisneria americana were only found in the shallow (<60 cm), oligohaline (<10 ppt) waters of Trinity Bay.Halophila engelmannii andThalassia testudinum were only found in the deeper (35–110 cm) euhaline waters (30–40 ppt) of Christmas and Matagorda Bays.H. wrightii andR. maritima occurred across the greatest depth and salinity spectra, withR. maritima more prominent in shallower (<90 cm) mixohaline waters (10–30 ppt) andH. wrightii more prominent in euhaline waters (30–40 ppt). Beds of SAV were more extensive and had greater biomass along south shorelines compared to north shorelines (P<0.045), and depth to which vegetation grew was positively correlated with water clarity (r=0.927, P<0.001). The correlations of water depth, salinity, and water clarity with variation in SAV species composition and distribution suggest that abiotic tolerances documented by previous experimental studies are major factors influencing field distributions. Comparisons with similar field data from the early 1970s corroborate the reported decrease in SAV in the Galveston Bay complex and suggest a slight increase in the Matagorda Bay complex. Decline of SAV in the Galveston Bay complex coincided with major shorefront development and a decline in numbers of wintering redhead ducksAythya americana. Protection of shorelines of upper coast estuaries is vital to maintaining SAV resources and the dependent fauna. Where possible, barrier island preserves should be established adjacent to beds of-SAV and development restrictions implemented to reduce impacts.

Phytoplankton composition and spatial distribution of copper and zinc in the Fal Estuary (Cornwall, UK)

In the estuaries near Falmouth (Cornwall, UK) levels of dissolved copper and zinc are high, due to drainage of copper and tin mines. Phytoplankton species composition in the autumn of 1989 deviated in the metal-contaminated Restronguet Creek from that in other estuarine branches,viz. Fal, Tresillian and Percuil. In the riverine part of Restronguet Creek (Carnon River)Euglena mutabilis, known as an acidophilic (pH 3) metal-resistant flagellate, occurred at micromolar Cu and Zn, whereas in the clean riversChlamydomonas sp. andOocystis sp. occurred at nanomolar Cu and Zn. An ordination analysis revealed the following patterns in Cu, Zn and phytoplankton species composition in the poly- and euhaline waters. Seston-bound Zn and dissolved Zn were in equilibrium,Katodinium rotundatum is Zn-tolerant, andSkeletonema costatum occurred in water with high contents of Cu in seston. However, none of the variables in these patterns correlated at a significant level (p>0.05). The results show that algae-metal interactions are complicated, and that statistical correlations foundin situ need experimental verification.