Levels Of Nutrient Enrichment Research Articles

Effects of nutrient enrichment on freshwater macrophyte and invertebrate abundance: A meta-analysis.

External nutrient loading can cause large changes in freshwater ecosystems. Many local field and laboratory experiments have investigated ecological responses to nutrient addition. However, these findings are difficult to generalize, as the responses observed may depend on the local context and the resulting nutrient concentrations in the receiving water bodies. In this research, we combined and analysed data from 131 experimental studies containing 3054 treatment-control abundance ratios to assess the responses of freshwater taxa along a gradient of elevated nutrient concentrations. We carried out a systematic literature search in order to identify studies that report the abundance of invertebrate, macrophyte, and fish taxa in relation to the addition of nitrogen, phosphorus, or both. Next, we established mixed-effect meta-regression models to relate the biotic responses to the concentration gradients of both nutrients. We quantified the responses based on various abundance-based metrics. We found no responses to the mere addition of nutrients, apart from an overall increase of total invertebrate abundance. However, when we considered the gradients of N and P enrichment, we found responses to both nutrients for all abundance metrics. Abundance tended to increase at low levels of N enrichment, yet decreased at the high end of the concentration gradient (1-10 mg/L, depending on the P concentration). Responses to increasing P concentrations were mostly positive. For fish, we found too few data to perform a meaningful analysis. The results of our research highlight the need to consider the level of nutrient enrichment rather than the mere addition of nutrients in order to better understand broad-scale responses of freshwater biota to eutrophication, as a key step to identify effective conservation strategies for freshwater ecosystems.

Artificial night‐time lighting and nutrient enrichment synergistically favour the growth of alien ornamental plant species over co‐occurring native plants

Abstract Insights into ecological drivers of alien plant invasions can be gained through comparative studies of growth and fecundity of invasive alien plants versus those of co‐occurring non‐invasive alien plants and native plants across environmental conditions in common garden settings. Habitats that harbour alien plant species in many ecosystems globally are presently experiencing light pollution resulting from artificial light at night (ALAN) and increased rates of nutrient enrichment of the soil. However, the potential interactive effects of ALAN and nutrient enrichment on invasiveness of alien plant species remain unknown. Here, we performed a common‐garden experiment to test the interactive effects of ALAN and soil nutrient enrichment on the growth of a random set of ten alien (five invasive and five non‐invasive naturalized) and seven co‐occurring native ornamental plant species that are commonly cultivated within urban and peri‐urban areas of Nairobi city in Kenya. We predicted that a simultaneous increase in photoperiod via ALAN and nutrient enrichment will favour growth of invasive alien plant species over that of non‐invasive alien and native plant species. We grew the 17 plant species under natural daylight (ALAN−) versus natural daylight followed by ALAN (ALAN+) and fully crossed with two levels of nutrient enrichment (low vs. high) and competition (competition vs. no‐competition against a native plant Ocimum gratissimum) treatments. Under simultaneous high‐nutrient and no‐competition treatments, ALAN enhanced mean total biomass of invasive and non‐invasive naturalized alien species by 61.1% and 131.4%, respectively but decreased that of native plant species by 34%. In contrast, under simultaneous high‐nutrient and competition treatments, ALAN enhanced mean total biomass of invasive alien plant species by 68.6% and that of non‐invasive naturalized alien species by 51.9% and native species by 35.4%. High‐nutrient treatment enhanced flower formation more strongly in invasive and non‐invasive naturalized alien plants than in native plants. The invasive and non‐invasive naturalized alien species grew taller than native species across the light, nutrient, and competition treatments. Synthesis: The present findings suggest that light pollution and nutrient enrichment may jointly confer growth advantage to invasive alien plant species over that of co‐occurring native plant species and enhance invasiveness of alien plant species.

Levels of nutrient enrichment determine the emergence of zooplankton from resting egg banks

Levels of nutrient enrichment determine the emergence of zooplankton from resting egg banks

Fish morphological and parasitological traits as ecological indicators of habitat quality in a Mediterranean coastal lagoon

Abstract Coastal lagoons are key ‘transitional’ aquatic environments for biodiversity conservation. Ecological indicators are useful tools for the management of water resources in the European Union. Among different biological communities, fish are a very sensitive tool to assess environmental integrity. Indeed, their parasites can be used as complementary indicators of habitat quality. Yet there is still a deep lack of information on ecological assessment using fish (along with their parasites) for coastal lagoons, particularly for the Iberian Peninsula. The aim of the present study was to assess the use of fish morphology and their parasite communities as ecological indicators of anthropogenic impact within the Mar Menor coastal lagoon (SE Spain), a Mediterranean area of special conservation concern for European/Iberian biodiversity. Fish samples (black‐striped pipefish Syngnathus abaster and marbled goby Pomatoschistus marmoratus) were collected in August 2022 from the Littoral (high level of nutrient enrichment) and Barrier habitats. Physical status (both external and internal indices), asymmetry (level of developmental instability), parasite load, diversity and life‐cycle complexity were compared between habitat types. Body condition and mainly the health assessment index were better in the Barrier habitat. Except for pectoral fins in pipefish, the fluctuating asymmetry was statistically greater in the Littoral habitat (i.e. with eutrophication leading to poorer fish development). The parasite load was higher in the Littoral habitat for both host fish species. However, the diversity and life‐cycle complexity of parasite communities were statistically lower in the Barrier habitat (a structurally simpler environment) only for gobies. This study demonstrates an elevated potential for certain fish morphological and parasitological traits to be considered as good ecological indicators of environmental health. This could help environmental managers and policy makers to design effective monitoring programmes to detect impacts within valuable areas for conservation, such as the Mar Menor coastal lagoon.

Nutrient enrichment drives the sediment microbial communities in Chinese mitten crab Eriocheir sinensis culture

Microbial communities play a critical role in aquaculture ecosystems. To identify the influence of sediment nutrient levels on microbial communities, sediment and water samples were collected from Chinese mitten crab Eriocheir sinensis culture ponds with different nutrient enrichment levels. Relevant physicochemical properties were measured, and 16 S rRNA gene sequencing was applied to identify relevant bacterial communities in the sediments. The results showed that the diversity and composition of microbial communities in sediments with different levels of nutrient enrichment varied considerably. Proteobacteria was the most abundant phylum in all samples, followed by Bacteroidetes, and Desulfobacterota with relative abundances of 23.5–40.9%, 9.8–21.5%, and 9.6–18.1%, respectively. Notably, total nitrogen (TN), organic matter (OM), and pH were important factors driving sediment bacterial community aggregation, the TN concentration explaining 61.5% of the microbial community variation. This study highlights that long-term culture activities alter the degree of sediment nutrient enrichment, which in turn affects microbial community composition and may ultimately have an impact on culture efficiency.

Opposite effects of nutrient enrichment and an invasive snail on the growth of invasive and native macrophytes.

Many ecosystems are now co-invaded by alien plant and herbivore species. The evolutionary naivety of native plants to alien herbivores can make the plants more susceptible to the detrimental effects of herbivory than co-occurring invasive plants, in accordance with the apparent competition hypothesis. Moreover, the invasional meltdown hypothesis predicts that in multiply invaded ecosystems, invasive species can facilitate each other's impacts on native communities. Although there is growing empirical support for these hypotheses, facilitative interactions between invasive plants and herbivores remain underexplored in aquatic ecosystems. Many freshwater ecosystems are co-invaded by aquatic macrophytes and mollusks and simultaneously experience nutrient enrichment. However, the interactive effects of these ecological processes on native macrophyte communities remain an underexplored area. To test these effects, we performed a freshwater mesocosm experiment in which we grew a synthetic native community of three macrophyte species under two levels of invasion by an alien macrophyte Myriophyllum aquaticum (invasion vs. no invasion) and fully crossed with two levels of nutrient enrichment (enrichment vs. no enrichment) and herbivory by an invasive snail Pomacea canaliculata (herbivory vs. no herbivory). In line with the invasional meltdown and apparent competition hypotheses, we found that the proportional aboveground biomass yield of the invasive macrophyte, relative to that of the native macrophyte community, was significantly greater in the presence of the invasive herbivore. Evidence of a reciprocal facilitative effect of the invasive macrophyte on the invasive herbivore is provided by results showing that the herbivore produced greater egg biomass in the presence versus in the absence of M. aquaticum. However, nutrient enrichment reduced the mean proportional aboveground biomass yield of the invasive macrophyte. Our results suggested that herbivory by invader P. canaliculata may enhance the invasiveness of M. aquaticum. However, nutrient enrichment of habitats that already harbor M. aquaticum may slow down the invasive spread of the macrophyte. Broadly, our study underscores the significance of considering several factors and their interactions when assessing the impact of invasive species, especially considering that many habitats experience co-invasion by plants and herbivores and simultaneously undergo various other disturbances, including nutrient enrichment.

An evolving marine environment and its driving forces of algal blooms in the Southern Yellow Sea of China

Continuing global warming and intensification of human activities have substantially disturbed the balance of coastal marine ecosystems, potentially creating favorable conditions for algal blooms. Using serial remote sensing data and various national and provincial statistics, we investigated the spatial and temporal variations of the environmental driving forces for algal blooms in the Southern Yellow Sea between 2003 and 2017. The findings suggest that (1) Continual warming was observed in the Southern Yellow Sea. The study area evidenced more than three times the warming speed (0.41 °C/decade) of the global oceans (0.12 °C/decade) during the same period. There was an apparent warming zone in the region where macroalgal blooms tended to spread, with a heating of 1.0–1.5 °C (May–June). (2) Nutrient loadings have diverse patterns, characterized by fast-growing aquaculture activities and declining nutrients from land-based agriculture fertilizers and sewage discharge (based on published national and provincial statistics). (3) Growing expansion of algal blooms in the Southern Yellow Sea was confirmed by the relative increases in average May–June chlorophyll-a concentration of 46.7% and floating biomass area from 3.3% in 2003 to 13.4% in 2017. (4) While spatial correlation analysis showed a positive influence of the ocean surface temperature on chlorophyll-a, their relatively moderate (r = 0.40, p < 0.15) and declining correlations suggest that nutrient enrichment could be comparatively more influential on macroalgal blooms. Nutrient loading from the discharge of wastewater sourced from coastal aquaculture and organic residuals from land-sourcing sewage and industrial pollution, even though declining as reported, is still upholding a high level of nutrient enrichment in the study area. In addition, the fixed facilities for seaweed mariculture in the region provide vast breeding surfaces for algae. Consequently, the Southern Yellow Sea has become an ideal marine area for algal blooms.

A New Classification Tool and a Systematic Review of Macroalgal Studies Disentangle the Complex Interactive Effects of Warming and Nutrient Enrichment on Primary Production

In order to understand how global warming effects on ecosystem primary production may change depending on nutrient enrichment, a new classification is proposed to disentangle and recognize the combination of interactions among several factors, based on the effect direction (positive, negative, or neutral) and its changes induced in it by the other factor (synergizing, antagonizing, inducing no change, or changing it in some other way). Marine macroalgae were chosen (as primary producers for which there is the most experimental information available) to review the relevant studies on which this new classification can be tested. It was observed the positive effects of elevated temperature and nutrient enrichment often synergized each other within the temperature range between relatively low and optimal growth levels. However, the negative effect of further temperature elevation from optimal to higher levels was antagonized by nutrient enrichment in some studies but was synergized in others, depending on the range of temperature elevation. The positive effect of nutrient enrichment was antagonized (but still positive) by temperature increase above the optimum in many cases, although the effect sometimes switched to a negative effect depending on the magnitude of nutrient enrichment. These results predict that global warming will enhance bottom-up effects on primary production in cold seasons and areas, and there will be a negative warming effect on production in hot seasons and areas, but it may be possible to mitigate this effect by appropriate levels of nutrient enrichment.

Nitrogen and phosphorus addition differentially enhance seed production of dominant species in a temperate steppe.

Previous studies have demonstrated changes in plant growth and reproduction in response to nutrient availability, but responses of plant growth and reproduction to multiple levels of nutrient enrichment remain unclear. In this study, a factorial field experiment was performed with manipulation of nitrogen (N) and phosphorus (P) availability to examine seed production of the dominant species, Stipa krylovii, in response to N and P addition in a temperate steppe. There were three levels of N and P addition in this experiment, including no N addition (0 g N m−2 year−1), low N addition (10 g N m−2 year−1), and high N addition (40 g N m−2 year−1) for N addition treatment, and no P addition (0 g P m−2 year−1), low P addition (5 g P m−2 year−1), and high P addition (10 g P m−2 year−1) for P addition treatment. Low N addition enhanced seed production by 814%, 1371%, and 1321% under ambient, low, and high P addition levels, respectively. High N addition increased seed production by 2136%, 3560%, and 3550% under ambient, low, and high P addition levels, respectively. However, P addition did not affect seed production in the absence of N addition, but enhanced it under N addition. N addition enhanced seed production mainly by increasing the tiller number and inflorescence abundance per plant, whereas P addition stimulated it by decreasing the plant density yet stimulating height of plants and their seed number per inflorescence. Our results indicate seed production is not limited by P availability but rather by N availability in the temperate steppe, whereas seed production will be increased by P addition when N availability is improved. These findings enable a better understanding of plant reproduction dynamics in the temperate steppe under intensified nutrient enrichment and can inform their improved management in the future.

Eutrophication reduces seagrass contribution to coastal food webs

AbstractFood sources and food web structure in seagrass meadows are important determinants of ecosystem functions and services. However, there is little information on the effect of eutrophication on food source contributions and food web structure in seagrass meadows. Here we used stable isotopes of carbon and nitrogen (δ13C and δ15N) to investigate how do different levels of nutrient enrichment affect the diets of consumers and food web structure within tropical seagrass meadows. We found that the diet contributions of macroalgae (mean 24% ± 12% for fish, 21% ± 5% for invertebrates), particulate organic matter (mean 19% ± 12% for fish, 18% ± 8% for invertebrates), and sediment organic matter (mean 24% ± 13% for fish, 21% ± 8% for invertebrates) to fish and invertebrates were all higher in seagrass meadows with higher nutrient concentrations, while seagrass and epiphytes contributed more to consumers in seagrass meadows with lower nutrient concentrations. Meanwhile, higher nutrient concentrations decreased the trophic position (mean 2.6 ± 0.5 in high‐nutrient level, 3.4 ± 0.6 in low‐nutrients level) of consumers and food chain length (2.5 in high‐nutrient level, 2.9 in low‐nutrients level). Higher nutrient concentrations reduced the contribution of seagrass carbon to consumers through the grazing food chain, but enhanced the flow of macroalgal carbon to consumers through the grazing food chain. Overall, eutrophication modified the food web structure of seagrass meadows. We recommend that measures be taken to decrease nutrient input into seagrass ecosystems to maintain its important functions and services.

EDNA reveals estuarine benthic community response to nutrient enrichment – evidence from an in-situ experiment

Nutrient loading is a major threat to estuaries and coastal environments worldwide, therefore, it is critical that we have good monitoring tools to detect early signs of degradation in these ecologically important and vulnerable ecosystems. We carried out a seven-month manipulative experiment in two estuaries to assess the effects of nutrient loading on benthic communities. Environmental DNA metabarcoding was used to examine the response of eukaryotic (18S rRNA), diatom (rbcL), and bacterial (16S rRNA) communities to two levels of nutrient enrichment (150 and 600 g N m-2). Multivariate analyses demonstrated consistent changes in eukaryotic, diatom, and bacterial communities in response to enrichment, despite differing environmental conditions between sites (Fig. 1). These patterns aligned with changes in macrofaunal communities identified using traditional morphological techniques, confirming concordance between disturbance indicators detected by eDNA and current monitoring approaches. Clear shifts in eukaryotic and bacterial indicator taxa were seen in response to nutrient loading while changes in diatom communities were more subtle. Community changes were discernable between nutrient levels, suggesting that estuary health assessment tools could be developed to detect early signs of degradation. Existing eDNA-based biotic indices (microgAMBI and mtMBI) were able to detect these community shifts, suggesting transferability of these indices to other regions and systems. This work represents a first step towards the development of molecular-based estuary monitoring tools, which could provide a more holistic and sensitive approach to ecosystem health assessment with faster turn-around times and lower costs.

Lentic chironomid performance in species-based bioassessment proving: High-level taxonomy is not a dead end in monitoring

Chironomid identification for freshwater bioassessment purposes is rarely finer than family or subfamily level. This has led to their taxonomic neglect and a lack of knowledge about their characteristics and ecology at the genus or species level, which in turn makes their implementation in bioassessment models even less appealing. The aim of this study was to object against this practice and evaluate the possibility of using chironomid assemblages solely in assessing organic and nutrient enrichment levels of lentic habitats. For this purpose, the littoral zone of 28 lentic water bodies of the Dinaric western Balkan ecoregion was sampled. Due to the scarcity of natural lakes in this region, resulting from its specific karst geology, both natural and artificial water bodies were included in this survey. Chironomids, determined mostly to species and genus level, were tested in response to variables associated with organic enrichment (dissolved organic carbon and oxygen demand measures) and nitrate concentration. A metric (Lake chironomid metric, LCM) based on 107 chironomid taxa was developed and proven to reflect organic enrichment more precisely than standard metrics that respond to organic enrichment (BMWP and different Saprobic indices). We found that the LCM strongly supports the use of chironomids with high taxonomic resolution in lentic habitat assessment, as we have shown that chironomids have the ability to improve, or even replace, already existing models for organic nutrient enrichment. We have also shown that chironomids can be used in assessing even finer levels of nitrate pollution with changes in community occurring at as low as 0.07 mgNO3−/l. This allows earlier intervention and hopefully prevention of considerable damage to the environment. We can conclude that chironomids (especially determined to species level) have great potential in monitoring of lake ecosystems.

Influence of nutrient enrichment on the growth, recruitment and trophic ecology of a highly invasive freshwater fish

The establishment probability of introduced alien fish can be context dependent, varying according to factors including propagule pressure and biotic resistance. The influence of nutrient enrichment on establishment outcomes of alien fishes is uncertain, yet this is a common anthropogenic stressor of many freshwaters. Here, the small-bodied alien topmouth gudgeon Pseudorasbora parva was used in mesocosms to experimentally test how a gradient of nutrient enrichment affected their growth rates, recruitment and trophic ecology. A ‘Control’ represented ambient, mesotrophic conditions, while treatments covered three levels of nutrient enrichment: low (eutrophic), medium (hypertrophic) and high (very hypertrophic). Each mesocosm was seeded with 6 mature P. parva (equal sex ratio) at the start of their reproductive season. After 100 days, length increments of the adult fish were significantly elevated in the low treatment, and these fish had also produced significantly higher numbers of 0+ fish compared to all other treatments. The trophic niche width of the mature fish was substantially higher in the control than the treatments, but this did not appear to confer any advantages to them in somatic growth rate or reproductive output. These results suggest that the nutrient status of receiving waters can have substantial impacts on the outcomes of fish introductions, where eutrophic conditions can assist the rapid population establishment of some alien species.

Is culture performance of juvenile sandfish, Holothuria scabra, in ocean-based nursery systems influenced by proximity to milkfish (Chanos chanos) farms and hapa net mesh size?

The impacts of proximity to milkfish farms (i.e. ‘close’, ‘intermediate’ and ‘distant’) and different hapa net mesh sizes (i.e. 400 μm and 1 mm) on periphyton characteristics and growth performance of sandfish, Holothuria scabra, juveniles (4.6 ± 0.1 mm), were evaluated in a 30-day field experiment in the Guiguiwanen Channel at Bolinao, North-western Philippines. Growth and survival of sandfish juveniles were determined twice, and chlorophyll a and ash-free dry weight (AFDW) of periphyton were monitored every 5 days during the study. Opisthobranchs that recruited inside the hapa nets were identified and counted during monitoring. Survival of sandfish juveniles differed significantly between sites but was not influenced by mesh size by day 15. Survival was significantly higher at the intermediate site by day 15. Juvenile survival was significantly higher in 400 μm mesh hapa nets across all sites by day 30. Result showed that mean length and absolute growth rates (AGR) of sandfish juveniles were significantly influenced by mesh size but not by site at day 15. Juveniles reared in the 1 mm mesh hapa nets were larger and grew faster by day 15. However, by day 30, mean length and AGR of sandfish juveniles were significantly affected by site but not mesh size. Juveniles reared at the close site were significantly larger and grew faster than those reared at the intermediate site while mean length and AGR of juveniles reared at the distant site were not significantly different to those cultured at either the close or intermediate sites. Growth rates of juveniles were lower on day 30 compared to day 15 possibly resulting from reduced food availability, as indicated by lower periphyton AFDW, resulting from inter- and intraspecific competition. A positive correlation was found between AGR and the number of surviving sandfish juveniles by day 15, while no correlation between the two parameters was observed by day 30 indicating that reduced growth rates were not mediated by interspecific stocking density, but most likely resulted from high intraspecific grazing pressure. Chlorophyll a content of periphyton was higher during the second half of the experiment; however, total periphyton biomass (as AFDW) generally decreased overtime. This reduced food availability coincided with the higher number of opisthobranchs in the hapa nets by day 30. Results showed that sandfish juveniles can grow in an environment with varying levels of nutrient enrichment, however, areas close to mariculture activity may support improved growth because of resulting increases in periphyton biomass. Additionally, the use of finer mesh (400 μm) hapa nets positively impacted juvenile survival and would support earlier transfer of juveniles from the hatchery to the ocean reducing husbandry inputs and costs.

Land-use intensity alters both the source and fate of CO2 within eight sub-tropical estuaries

Combined pressures from inland agricultural intensification and coastal development are dramatically altering estuaries’ structure and function. Despite the established global significance of estuarine carbon (C) cycling, the impact of growing anthropogenic stress on coastal C inputs and exports is unclear. To address this gap, we evaluated the magnitude and drivers of estuary C fluxes in eight sub-tropical estuaries at Low (n = 3), Moderate (n = 2), and High (n = 3) levels of nutrient enrichment. We measured changes in the concentration and isotopic composition (δ13C) of the major C pools (organic and inorganic) and gaseous product of C turnover (CO2) over wet and dry seasons. Over both sampling periods estuaries classified Moderate and High emitted far more CO2 (37 ± 10 mmol m−2 d−1) than those classified Low (6.3 ± 4 mmol m−2 d−1). However, estuaries with both high nutrients and high turbidity produced less CO2, and thus exported more DIC, than expected from hydrodynamics (freshwater flushing time). Differences in estuary phytoplankton biomass (Chla concentrations) corresponded with differences in the biological CO2 production (respiration) rates estimated from δ13C-DIC variations, although respiration rates were higher than predicted based on hydrodynamics (surface area/discharge) in high nutrient, low turbidity systems. Together these findings demonstrate that land-use intensification can alter both the source and the production of estuary CO2, and suggest that the direction of this shift can depend on ancillary factors like turbidity as well as nutrient enrichment. Evidence that human alterations to coastal ecosystems can shift the balance between DIC downstream export and CO2 emissions outside of the range predicted by hydrodynamic factors like residence time, surface area, and discharge has implications for global C models.

The independent effects of nutrient enrichment and pulsed nutrient delivery on a common wetland invader and its native conspecific.

Human activities often lead natural systems to be nutrient enriched, with anthropogenically derived nutrients commonly delivered in discrete pulses. Both nutrient enrichment and nutrient pulses can impact plant performance and phenotypic plasticity, especially in invasive species, but quantifying their independent effects remains challenging. To explore the effects of nutrient enrichment and nutrient pulse magnitude, we established a common garden experiment using the North American wetland invader Phragmites australis and its native conspecific Phragmites australis subsp. americanus (five source populations each). We exposed plants to three levels of nutrient enrichment that were delivered either in small or large-magnitude pulses, examining productivity and plasticity responses over a single growing season. Productivity and biomass allocation differed by lineage, with invasive Phragmites producing 73% more biomass and 66% more culms, but with the native growing 31% taller and allocating more of its biomass belowground. Contrary to expectations, both lineages responded similarly to nutrient enrichment and were similarly plastic in their traits. Nutrient enrichment, rather than nutrient pulses, led to large productivity gains and trait plasticity magnitudes. However, total biomass and leaf-level traits (specific leaf area and chlorophyll concentration) were responsive to variation in nutrient pulse magnitudes. By decoupling the effects of nutrient enrichment from nutrient pulses, our study demonstrates the independent effects of these two key factors for plant performance and, by extension, invasion success. We report trait-based similarities between two lineages of Phragmites that play contrasting ecological roles in North American wetlands, and we highlight the potentially detrimental effects of nutrient pulses.

Application and comparison of two symptom-based eutrophication-assessment methods in Jiaozhou Bay, China

Increasing numbers of approaches to assess eutrophication, such as estuarine trophic status, the Oslo-Paris Commission Common Procedure, and the Water Framework Directive, focus on the symptoms of eutrophication. In China, however, nutrient index methods dominate the assessment of coastal waters. In this study, an integrated method that includes both water quality and ecological response was compared with the Northwest Pacific Action Plan (NOWPAP) Common Procedure. Observation data from Jiaozhou Bay, Shandong, China, were used in a comparison of the two methods in a trophic status study. Overall, both clearly revealed a high level of nutrient enrichment in the bay, indicated by high nutrient concentrations. Though the two methods differed in their methodological design in the assessment of the ecological effects of nutrient enrichment, they have acquired similar results: the integrated method suggested that the status was good, and the NOWPAP Common Procedure suggested that the status was low (indicating that the bay had no serious eutrophication problem). The introduction of filter feeders (shellfish aquaculture) into the bay on a reasonable scale may have been effective in mitigating eutrophic conditions, and perhaps explains the low ecological impacts there. Our results will be useful to ecosystem-based eutrophication management in the bay and in similar areas.

Marinas: An overlooked habitat for exploring the relation among polychaete assemblages and environmental factors

The increasing number of anthropogenic areas in the marine environment results in significant impact to adjacent ecosystems. In fact, the presence of marinas modifies the original environmental conditions and ends up disturbing the faunal community. However, despite the essential role displayed by the macrofauna on marinas' fouling biota, certain taxa such as polychaetes have been poorly studied. The present study provides the first spatial characterization of the epibiont polychaete fauna associated with the bryozoan Bugula neritina in marinas along the Iberian Peninsula and the north of Morocco. A total of 32 polychaete species were identified, with Syllidae being the most diverse family. Furthermore, the environmental factors involved in the occurrence and abundance of the dominant species Salvatoria clavata were also analyzed by Generalized Linear Models; results showed that the highest predicted values of S. clavata abundance appeared at marinas with high levels of nutrient enrichment and of heavy metals concentration.

No difference in ectomycorrhizal morphotype composition between abandoned and inhabited nests of wood ants (Formica polyctena) in a central European spruce forest

In temperate forest ecosystems, ectomycorrhizal (EcM) fungi substantially support coniferous trees by nutrients, but importance of EcM for tree nutrition might be lower in nutrient-rich hotspots, such as in wood ant nests. In this study, we focused on differences in EcM morphotype composition between natural nutrient-rich hot spots of various quality (inhabited vs. abandoned wood ant nests) and the surrounding forest floor. In a secondary Norway spruce forest typical for central Europe, we took samples from different belowground parts of five inhabited and five abandoned nests (centre and rim) as well as from the forest floor 20 cm from the nests (run-off zone) and >3 m from the nests (forest soil). The substrates were subjected to analyses of the EcM morphotype composition, moisture and nutrient contents. Wood ant nest substrates had several times increased nutrient contents compared to the forest soil, but there were no significant differences in moisture. Available nutrient contents were higher in inhabited nests than in abandoned nests. The EcM morphotype composition differed between the nest samples and the forest floor samples but not between the inhabited and abandoned nests suggesting that, apart from the level of nutrient enrichment and their availability, moisture is another important factor affecting EcM community composition.

Macroalgal composition and accumulation in New England estuaries

New England estuaries provide essential feeding grounds and nursery habitat for important recreational and commercial species. However, these functions are being altered by a recent shift in estuarine plant dominance from rooted plants to opportunistic drift macroalgae that can form dense accumulations. We hypothesize that formation of these macroalgal accumulations is controlled by the level of nutrient enrichment and the low hydrodynamic energy regime present in many estuarine basins. To test this hypothesis, we conducted temporal macroalgae surveys in eight s.e. Massachusetts estuaries to quantify the level of accumulation within basins with varying levels of nitrogen enrichment and bottom currents. Our results indicate that opportunistic Ulva spp. dominated the macroalgal community in both estuaries with temporal surveys, Green and Great Ponds. Measurements of tidal transport revealed a net import of macrophyte material but with no import or export of Ulva. Within each estuary, occurrence of opportunistic macroalgae was positively related to levels of water column total nitrogen (R2 = 0.76) and growth rate of Ulva spp. directly related to total nitrogen + light level (R2 = 0.92), while bottom coverage was >20% at TN levels >0.48 mgL−1. We conclude that opportunistic species accumulate in response to nutrient enrichment with in situ processes controlling growth and decay, while import and tidal transport play relatively minor roles in the distribution of opportunistic drift macroalgae in these shallow estuaries.