The Relationship between Phytoplankton Distribution and Water Column Characteristics in North West European Shelf Sea Waters (original) (raw)
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Diatom assemblages as indicators of salinity gradients: a case study from a coastal lake
Oceanological and Hydrobiological Studies, 2017
In order to understand the variability of diatoms in coastal lakes and its relationship to salinity, the authors have conducted a two-year study at Lake Resko Przymorskie (the Southern Baltic coast), which has a salinity between 1.9-4.8 PSU. Redundancy analysis (RDA) was used to describe the relationship between the species composition and selected variables. Four of the 10 measured variables of surface water chemistry (Cl- and PO4 3- concentrations, temperature, and pH) significantly explained 23% of the variation in the diatom species composition. We found 82 taxa of diatoms (mostly tychoplanktonic) and determined the optimum and tolerance levels of salinity for predominant taxa (49 species with minimum 2% abundance). The optimum chloride concentration for the predominant diatoms ranged from 1471 to 2961 mg Cl- l-1. The most abundant brackish water species was Pseudostaurosiropsis geocollegarum. Brackish-freshwater diatoms were represented by Cyclotella atomus, Cyclotella meneghin...
Hydrobiologia, 2008
The implementation of the European Water Framework Directive (WFD) requires the development of ecologically-based classification systems for anthropogenically-induced eutrophication in all types of water bodies. Due to the inherent high temporal and spatial variability of hydrological and geochemical parameters of the coastal waters of the southern Baltic Sea, discrimination between anthropogenic impact and natural variability is necessary. The development of statistical methods for this discrimination was the main aim of this study. These methods were used to derive indicative phytoplankton parameters for different stages of eutrophication for the investigation area. For this purpose, a long-term phytoplankton data series was analysed, which covered a broad salinity and eutrophication gradient. In order to detect eutrophication effects, the analysis was restricted to phytoplankton spring bloom events and to the salinity range between 5 and 10 psu, i.e. superimposing seasonal and hydrodynamic effects were eliminated. An artificial abiotic degradation vector was developed based on four typical water quality parameters. A total of 11 potentially indicative phytoplankton parameters on different taxonomical levels arose from a correlation analysis with this degradation vector. These indicators were then tested for their ability to discriminate between three eutrophication levels. Finally, seven phytoplankton indices could be proposed: total phytoplankton biovolume, the percentage of diatoms and the biovolume of different size ranges of diatoms and one indicative species (Woronichinia compacta).
Coastal Diatom-Environment Relationships from the Gulf of Finland, Baltic SEA1
Journal of Phycology, 2006
Eutrophication of the Baltic Sea has become a serious concern in recent decades. To provide a potential means for quality assessments of coastal waters in this area, we collected a data set of 49 embayments in the Gulf of Finland, and explored the relationship between surface sediment diatom assemblages and 15 environmental variables, with special emphasis on nutrients. Total dissolved nitrogen, total phosphorus, depth, and salinity all accounted for significant and independent fractions of variation in the diatom data and explained 34% of the total variation. There were clear changes in diatom assemblage structures along the nutrient gradients. Although these changes were gradual, we could identify a number of taxa that were more abundant in a particular nutrient environment. These taxa could be used as potential indicators of the quality of coastal waters in the Baltic Sea. Diatom assemblages that were least affected by nutrient enrichment included a variety of benthic species and a relatively high species richness. Small planktonic taxa such as Cyclotella atomus Hustedt, Cyclotella meneghiniana Kützing and Thalassiosira pseudonana Hasle and Heimdal were good indicators of highly elevated nutrient concentrations (4600 lg . L À 1 total dissolved nitrogen and 60 lg . L À 1 total phosphorus) together with low species richness. The first appearance of these small planktonic taxa in regular monitoring could be used as an early warning sign for deteriorating water quality. Diatoms could be applied to water quality classification and monitoring purposes in the coastal waters of the Baltic Sea area using techniques such as weighted-averaging regression and calibration.
Marine waters in general and coastal areas in particular suffer globally from stressing events. These events can be largely attributed to higher levels of human-induced eutrophication, contamination by pollutant, and siltation. The European Union and other countries have adopted legislation to guide monitoring efforts and set goals for good quality coastal environments. Few biological quality elements were identified by legislators for their ability to detect and identify sources of ecosystem perturbations. Research programs have developed indices calculation methods for benthic invertebrate fauna, phytoplankton, macroalgae and angiosperms. Most of these indices are multimetric, based on the richness, abundance and biomass of the community. Such indices determine the quality at one site after observational comparison with a reference situation. Functional indices, however, are based on species ecological preferenda and autoecology. Since species are generally response-specific, functional index allows the discernment of the stressing factor involved in the ecosystem perturbation. The final index value provides a direct appreciation of the ecological status of the study site. At the present time, there are few functional indices that can be used on a routine basis for monitoring coastal waters. Because biological quality elements cited below are not available in all areas, the range of monitoring is restricted to particular environments. This review paper suggests that marine benthic diatoms (Bacillariophyceae) may result in a functional index. Arguments for the use of these organisms as bio-indicators include knowledge from the past and present use of diatoms in freshwater environmental analysis. Marine benthic diatoms are abundant and ubiquitous in terms of ecosystems and water chemistry and are sensitive to nutrient variation, as revealed by two studies conducted in mesotrophic and oligotrophic areas. This review is focused on benthic diatoms and reveals that no study has yet been conducted on the use of these organisms as bio-indicators. Aspects of practical sampling and sample treatment for marine diatoms are considered. As the bio-indication role of diatoms is little explored in marine environments, the dataset on ecological indicator values of species is scarce. Future work that relates to taxonomic determination and physico-chemical description of sites are needed to better define species ecological preferenda, prior to the development of a marine diatom biotic index.
Journal of Experimental Marine Biology and Ecology, 2007
Effects of nutrients on the size and composition of phytoplankton and the resulting changes in ecosystem structure were investigated using incubations of unaltered deep-sea waters from 400 m and 700 m depths of Suruga Bay Japan. This new approach allowed us to observe the succession of phytoplankton communities from conditions of high to low nitrogen availability and explore the effects of N source and availability on the composition and size of diatoms under low grazing pressure. Diatoms dominated the phytoplankton biomass throughout the duration of experiments in both incubations. However, among diatoms, the genus Thalassiosira dominated the abundance and biomass when nutrients were replete, and the genus Chaetoceros dominated the abundance and biomass when nitrate became depleted. Our results show that diatoms can dominate other phytoplankton groups not only under nutrient replete conditions, but also (particularly for Chaetoceros) under low concentrations of recycled nitrogen if silica and phosphate are not deficient. Diatoms b 15 μm dominated the biomass in the 700 m incubation whereas those N 15 μm dominated the biomass in the 400 m incubations during the formation of blooms under nitrate-replete conditions. After nitrate depletion, diatoms N 15 μm dominated the biomass in both incubations. Our results showed that availability of N determined the composition of diatoms if Si and P are not deficient. However, for size the results showed that N source and availability did not determine the size of phytoplankton. Our results also showed that the molar ratio of Si:N uptake was b 1 for diatoms under nutrient replete conditions. Further the Si:N drawdown ratio decreased with the increasing abundance of smaller diatoms (b 15 μm).
Emerging phylogeographic perspective on the toxigenic diatom genus Pseudo-nitzschia in coastal northern European waters and gateways to eastern Arctic seas, 2023
The diatom Pseudo-nitzschia H. Peragallo is perhaps the most intensively researched genus of marine pennate diatoms, with respect to species diversity, life history strategies, toxigenicity, and biogeographical distribution. The global magnitude and consequences of harmful algal blooms (HABs) of Pseudo-nitzschia are particularly significant because of the high socioeconomic impacts and environmental and human health risks associated with the production of the neurotoxin domoic acid (DA) among populations of many (although not all) species. This has led to enhanced monitoring and mitigation strategies for toxigenic Pseudo-nitzschia blooms and their toxins in recent years. Nevertheless, human adaptive actions based on future scenarios of bloom dynamics and proposed shifts in biogeographical distribution under climate-change regimes have not been implemented on a regional scale. In the CoCliME (Co-development of climate services for adaptation to changing marine ecosystems) program these issues were addressed with respect to past, current and anticipated future status of key HAB genera such as Pseudo-nitzschia and expected benefits of enhanced monitoring. Data on the distribution and frequency of Pseudo-nitzschia blooms in relation to DA occurrence and associated amnesic shellfish toxin (AST) events were evaluated in a contemporary and historical context over the past several decades from key northern CoCliME Case Study areas. The regional studies comprised the greater North Sea and adjacent Kattegat-Skagerrak and Norwegian Sea, eastern North Atlantic marginal seas and Arctic gateways, and the Baltic Sea. The first evidence of possible biogeographical expansion of Pseudo-nitzschia taxa into frontier eastern Arctic gateways was provided from DNA barcoding signatures. Key climate change indicators, such as salinity, temperature, and water-column stratification were identified as drivers of upwelling and advection related to the distribution of regional Pseudo-nitzschia blooms. The possible influence of changing variables on bloom dynamics, magnitude, frequency and spatial and temporal distribution were interpreted in the context of regional ocean climate models. These climate change indicators may play key roles in selecting for the occurrence and diversity of Pseudo-nitzschia species within the broader microeukaryote communities. Shifts to higher temperature and lower salinity regimes predicted for the southern North Sea indicate the potential for high-magnitude Pseudo-nitzschia blooms, currently absent from this area. Ecological and socioeconomic impacts of Pseudo
Ecological Indicators, 2004
Abundance-weighted averages of diatom indicator values for pH, salinity, organic nitrogen availability, oxygen saturation, saprobity and trophic status according to van Dam et al. [Neth. J. Aquat. Ecol. 28 (1994) 117] were calculated for surface sediment and epiphytic diatom assemblages in 186 standing waters distributed throughout Flanders, Belgium, and tested against environmental variables measured in the water column, covering water chemistry, trophic status and organic load. With exception of the pH indication, most scores related rather poorly to variables which they are assumed to reflect and correlated even more strongly to non-target variables. For instance, the trophic indication provided a measure of pH and base status rather than of nutrient levels or phytoplankton productivity. Relations to measured variables differed according to the pH regime. Correction for uneven distribution of indicator values in the species pool usually yielded little improvement and was detrimental in some cases. Compared to epiphyton, weighted averages of species indicator values derived from sediment assemblages tended to be higher in water bodies yielding the most elevated indication scores. Except for the pH and salinity indication, differences between weighted averages pertaining to these different habitats were often considerable. Limitations to the use of abundance-weighted averages of diatom indicator values for environmental monitoring and assessment of lentic waters are discussed. # L. Denys / Ecological Indicators 4 (2004) 255-275 270 Fig. 4. Residuals of sediment-derived to epiphyton-derived indication scores (DmI) against sediment-derived abundance-weighted averages of species indicator values. Trend lines are a LOWESS smooth (stiffness 0.25).
Abundance and biomass estimates are metrics usually taken for phytoplankton assays. Biomass is a proxy measure today in phytoplankton assays, while relative abundance is broadly used in diatoms investigations and application of ecological indexes. The question is how the two metrics respond to environmental conditions, based on diatoms species composition, in the plankton of lotic system, using the same statistical approach. The investigation was carried out based on monthly plankton sampling in four rivers during an annual cycle in southern Brazil. Relative abundance and relative biomass of diatoms showed distinct responses for each river, and the dominant species according to each metric were different. Relative abundance significantly correlated with seven of the eight physical and chemical variables, while relative biomass did not. Both metrics were appointed to the major diatom species of each river, but biomass showed low statistic robustness. The analysis with higher taxonomic rank (families) yielded more coherent outcomes between the metrics. The results showed that diatom relative abundance is effective to relate the composition to environmental conditions; therefore, the abundance should not be neglected in studies of phytoplankton structure and dynamics, mainly when the diatoms are dominant in the community, and the low taxonomic rank ecological indication is regarded.
Assessments of the environmental status of the Baltic Sea as called for by the Marine Strategy Framework Directive (MSFD) must be based on a set of indicators. A pre-core indicator is the diatom/dinoflagellate index (Dia/Dino index), which reflects the dominance of diatoms or dinoflagellates during the phytoplankton spring bloom. Here we explain the principles of the Dia/Dino index and the conditions for its calculation using examples from two very different water bodies, the Eastern Gotland Basin and Kiel Bay. The index is based on seasonal mean diatom and dinoflagellate biomass values. A precondition for its applicability is the coverage of the bloom. As a criterion, the maximum value of diatom or dinoflagellate biomass has to exceed a predefined threshold, e.g., 1000 µg/L in the investigated areas. If this condition is not fulfilled, an alternative Dia/Dino index can be calculated based on silicate consumption data. Changes in the dominance of these two phytoplankton classes impact the food web because both their quality as a food source for grazers and their periods of occurrence differ. If diatoms are dominant, their rapid sinking reduces the food stock for zooplankton but delivers plenty of food to the zoobenthos. Consequently, the Dia/Dino index can be used to follow the food pathway (Descriptor 4 of MSFD: " food web "). Moreover, a low Dia/Dino index may indicate silicate limitation caused by eutrophication (Descriptor 5 of MSFD: " eutrophication "). The Dia/Dino index was able to identify the regime shift that occurred at the end of the 1980s in the Baltic Proper. Diatom dominance, and thus a high Dia/Dino index, are typical in historical data and are therefore assumed to reflect good environmental status (GES). In assessments of the environmental status of the Eastern Gotland Basin and Kiel Bay, Dia/Dino index GES thresholds of 0.5 and 0.75, respectively, are suggested. The GES thresholds as calculated by the alternative Dia/Dino index are 0.84 and 0.94, respectively.
AMBIO: A Journal of the Human Environment, 2007
Increased nutrient and sediment loading can affect the functioning and biodiversity of coastal ecosystems. Lacking long-term monitoring data, paleolimnological techniques enable the estimation of habitat and diversity change through time. Using these methods we assessed the effects of eutrophication on diatom community structure and species richness over the past ca. 200 years in coastal waters of the Gulf of Finland. The abundance of planktonic diatoms has increased markedly because of increased eutrophication and turbidity. The loss of benthic habitats resulted in a clear decrease in diatom species richness after a threshold of 400-600 lg L À1 total dissolved nitrogen; no unimodal pattern between diversity and productivity was observed in our data. The urban sites displayed a marked decrease in species richness starting in the late 19th century with increased urbanization. A clear recovery was visible after the cessation of point source loading by the mid-1980s at two sites, whereas at the third site no recovery was detected because of diffuse loading from the large catchment. Changes in the rural sites were minor and did not start until the 1940s.