Marine-derived Nutrients Research Articles

Combining hydrological investigations and radium isotopes to understand the environmental effect of groundwater discharge to a typical urbanized estuary in China

Pollution of urbanized rivers with excess nutrients due to groundwater discharge is an increasing environmental concern worldwide. Dan'ao river, a typical urbanized river in the Guangdong-Hong Kong-Macao Greater Bay Area, is experiencing heavy water pollution. However, the groundwater-derived nutrient loads had not yet been thoroughly quantified. In order to quantify the contribution of groundwater-derived nutrient inputs, we combined the methods of hydrological investigations and radium isotopes. Groundwater and river water samples were collected from the river upstream to the estuary for the analyses of radium quartets and nutrients including DIN, DIP and DSi. The results showed that the radium activities in both surface water and groundwater decreased from the estuary to the upstream. The groundwater discharge rate was estimated by the radium mass balance model using short-lived radium isotopes (223Ra and 224Ra). The estimated groundwater discharge rate ranged from 1.99 × 105 to 6.67 × 105 m3 d−1, comparable to the upstream river discharge rate of 4.23 × 105 m3 d−1. The groundwater-derived nutrient fluxes were 165.66–554.98 mmol m−2 d−1 for DIN, 2.47–8.26 mmol m−2 d−1 for DIP and 63.73–213.49 mmol m−2 d−1 for DSi, respectively. They contributed 19%~44% DIN, 16%~39% DIP, and 31%~60% DSi of all the nutrient inputs into the Dan'ao River, respectively. In addition, the nutrient inputs by groundwater discharge has an average DIN:DIP ratio of as high as 190, which is able to potentially affect the riverine and marine nutrient structures. These findings may provide useful information for designing control strategies for reducing massive nutrient inputs to Dan'ao River in the future.

Silicon isotopes in Arctic and sub-Arctic glacial meltwaters: the role of subglacial weathering in the silicon cycle

Glacial environments play an important role in high-latitude marine nutrient cycling, potentially contributing significant fluxes of silicon (Si) to the polar oceans, either as dissolved silicon (DSi) or as dissolvable amorphous silica (ASi). Silicon is a key nutrient in promoting marine primary productivity, contributing to atmospheric CO2 removal. We present the current understanding of Si cycling in glacial systems, focusing on the Si isotope (δ30Si) composition of glacial meltwaters. We combine existing glacial δ30Si data with new measurements from 20 sub-Arctic glaciers, showing that glacial meltwaters consistently export isotopically light DSi compared with non-glacial rivers (+0.16‰ versus +1.38‰). Glacial δ30SiASi composition ranges from −0.05‰ to −0.86‰ but exhibits low seasonal variability. Silicon fluxes and δ30Si composition from glacial systems are not commonly included in global Si budgets and isotopic mass balance calculations at present. We discuss outstanding questions, including the formation mechanism of ASi and the export of glacial nutrients from fjords. Finally, we provide a contextual framework for the recent advances in our understanding of subglacial Si cycling and highlight critical research avenues for assessing potential future changes in these environments.

Bottom-Up Effects on Coastal Marine Ecosystems Due to Nitrogen Input from Seabird Feces

Breeding seabirds, often nest at high densities and supply large amounts of marine-derived nutrients, such as nitrogen, in their feces into the ecosystems surrounding their breeding colonies. It has been well demonstrated that the nitrogen supplied by seabirds (seabird-N) into terrestrial ecosystems has a strong bottom-up effect on both producers and consumers. The seabird-N can reach into the surrounding marine ecosystems near the colony through multiple pathways including the surface run-off of rainwater or leaching by ground water. However, in marine ecosystems the bottom-up effects of seabird-N have been rarely documented. A few studies using stable isotope analyses have reported that seabird-N enhances the productivity of both phytoplankton and macro algae. There have been more limited studies documenting similar positive effects of seabird-N on marine consumers. Very little is known about spatio-temporal variations in the effects of the seabird-N on marine ecosystems. To understand the ecosystem functions of seabirds in marine nutrient cycling and the bottom-up effects of seabird-N in marine ecosystems, further research is necessary.

Application of the Spline Interpolation in Simulating the Distribution of Phytoplankton in a Marine NPZD Type Ecosystem Model.

The available observations for the model are usually sparse and uneven. The application of interpolation methods help researchers obtain an approximate form of the original data. A marine nutrient, phytoplankton, zooplankton and detritus (NPZD) type ecosystem model is applied to simulate the distribution of phytoplankton combined with the spline interpolation (SI) and the Cressman interpolation (CI). In the idealized twin experiments, the performance of these two interpolation methods is validated through the analysis of several quantitative metrics, which show the minor error and high efficiency when using the SI. Namely, the given distributions can be better inverted with the SI. The actual distribution of phytoplankton in the Bohai Sea is interpolated in the practical experiment, where a satisfactory simulation result is obtained by the model with the SI. The model experiments and results verify the feasibility and effectiveness of SI.

Nitrogen isotope evidence for stepwise oxygenation of the ocean during the Great Oxidation Event

Abstract The Earth’s oxygenation represents one of the most important environmental drivers of life’s evolution, with the first rise, known as ‘the Great Oxidation Event’ (GOE), corresponding to unpreceded accumulation of atmospheric O2, changes in the flux of marine nutrients and possibly global glaciations. However, the detailed evolution of the GOE is still debated, as for instance the accumulation trends of oceanic versus atmospheric oxygen and the nature of biogeochemical responses to oxygenation. Here, we combine organic carbon and bulk nitrogen isotope compositions with major element concentrations and iron speciation data of sedimentary rocks recovered from two drill cores (T2 and T3) in the early Paleoproterozoic Turee Creek Group, Western Australia, to track the redox evolution of marine conditions during the GOE. T2 core samples of the Kungarra Formation, which consists of clastic sedimentary rocks overlaid by the glaciogenic Meteorite Bore Member, were deposited ∼2.31 Ga ago. T3 core intercepts, from bottom to top, quartzite of the Koolbye Formation, and shales and stromatolitic carbonates of the Kazput Formation, which were deposited around ∼2.25 Ga. Samples from T2 show minor variations of δ13Corg (avg. −34.5 ± 1.7‰, n = 30), with no significant difference between siliciclastic and glaciogenic sedimentary rocks. In contrast, T3 samples display an increase in δ13Corg from −32.0 to −24.8‰ (n = 54) from shales to carbonates. In both T2 and T3 cores, δ13Corg values are inversely correlated with Al2O3, suggesting a strong petrological control on δ13Corg values, inferred here as resulting from variable contributions of detrital organic matter. Bulk N contents are low, from 13.5 to 56.7 ppm and 15.7 to 53.4 ppm in T2 and T3 samples, respectively. The δ15N values show a bimodal distribution, with one mode at +2.6‰ in T2 and another at +8.8‰ in T3, independent from lithological variations. This δ15N values shift between T2 and T3 is interpreted as reflecting a change from dominating N2-fixers to NO3-assimilating organisms. This implies an increase of NO3− availability, and thus of O2 concentration, during the time interval separating the deposition of T2 and T3 sediments. Dissolved NO3− and O2 concentrations of the Turee Creek marine basin are estimated from two models using N isotope data. The dissolved NO3− concentration has an upper limit ranging from 1.91 to 3.04 µM, about one order of magnitude below the average value of modern oceans. The lower limit for dissolved oxygen concentration ranges from 1.8 to 4.4 µM, which is two orders of magnitude lower than modern oceans. Together with previous studies, the present data place quantitative constraints on the redox changes associated with the Great Oxidation Event and illustrate a stepwise increase of NO3− bioavailability between 2.31 to 2.25 Ga, in relation with increasing O2 level.

Controls of plant diversity and composition on a desert archipelago.

AimWith the most robust floristic data set for any arid archipelago, we use statistical modeling to determine the underlying controls of plant diversity and species composition.LocationThe study was undertaken in the Midriff Islands of the Gulf of California, Mexico.MethodsUsing the area–diversity relationship we estimate the power coefficient z with generalized linear models (GLM). We tested eight predictors (area, human presence, habitat diversity, topography, distance to mainland, island type, precipitation, and seabird dynamics) using a step-wise process on the same GLM procedure. Plant species composition was assessed by conducting a non-standardized principal component analysis on a presence-absence matrix of the 476 (plant species) × 14 (islands). Finally, families were tested for over or under representation with a X2 analysis subjected to a Bonferroni correction.ResultsThe classic species-area model explained 85% of the variance in island plant diversity and yielded a slope (z) of 0.303 (±0.01). When the effect of area is removed, four additional factors were shown to account for observed variation; habitat diversity (34%), seabird dynamics (23%), island type (21%), topography (14%). Human presence and distance to mainland were not predictors of species richness. Species composition varies significantly with island area; small islands have a particular flora where certain families are overrepresented, such as Cactaceae, while the flora of larger islands is strongly dependent on the continental source.Main conclusionsThe factors that control diversity levels are expressions of geology, landscape heterogeneity, and land-sea connections. Species assemblages in small islands are governed by copious marine nutrients in the form of guano that depress species diversity. Distance to mainland and human presence hold no predictive power on diversity. The results show these islands to be isolated arid ecosystems with functioning ecological networks.

Microplastics alter feeding selectivity and faecal density in the copepod, Calanus helgolandicus

Microplastics (1 μm–5 mm) are a ubiquitous marine contaminant of global concern, ingested by a wide range of marine taxa. Copepods are a key component of marine food webs, providing a source of food for higher trophic levels, and playing an important role in marine nutrient cycling. Microplastic ingestion has been documented in copepods, but knowledge gaps remain over how this affects feeding preference and faecal density. Here, we use exposure studies incorporating algal prey and microplastics of varying sizes and shapes at a concentration of 100 microplastics mL−1 to show: (1) prey selection by the copepod Calanus helgolandicus was affected by the size and shape of microplastics and algae they were exposed to; Exposure to nylon fibres resulted in a 6% decrease in ingestion of similar shaped chain-forming algae, whilst exposure to nylon fragments led to an 8% decrease in ingestion of a unicellular algae that were similar in shape and size. (2) Ingestion of microplastics with different densities altered the sinking rates of faecal pellets. Faeces containing low-density polyethylene sank significantly more slowly than controls, whilst sinking rates increased when faeces contained high-density polyethylene terephthalate. These results suggest that C. helgolandicus avoid ingesting algae that are similar in size and/or shape to the microplastic particles they are exposed to, potentially in a bid to avoid consuming the plastic.

Bridging the Gap Between Salmon Spawner Abundance and Marine Nutrient Assimilation by Juvenile Salmon: Seasonal Cycles and Landscape Effects at the Watershed Scale

Anadromous Pacific salmon are semelparous, and resource subsidies from spawning adults (marine-derived nutrients, or MDN) benefit juvenile salmonids rearing in freshwater. However, it remains unclear how MDN assimilation relates to spawner abundance within a watershed. To address this, we examined seasonal, watershed-scale patterns of MDN assimilation in rearing coho (Oncorhynchus kisutch) and Chinook (O. tshawytscha) salmon and compared it with spawner biomass and landscape features in a western Alaska watershed with contrasting structural complexity in two sub-drainages. Adult salmon biomass density was estimated from escapement and spawner distribution data, and MDN assimilation in juvenile salmon was estimated via stable isotopes. In the North River, MDN assimilation was lowest in early summer, prior to annual spawning migrations, increased after spawning, and peaked in late winter. In the more complex mainstem Unalakleet River, MDN assimilation was higher but varied minimally from summer through fall before increasing in late fall and winter. Summer MDN assimilation, prior to salmon spawning, was primarily a function of habitat complexity, where MDN was highest in sloughs and the more complex mainstem river. After salmon spawned, fall MDN assimilation was a function of adult pink and Chinook salmon biomass as well as MDN assimilation that occurred prior to spawning (that is, summer MDN), but unrelated to total summer biomass (all salmon species biomass combined). Thus, MDN assimilation by juvenile salmon in the fall was a function of species-specific adult spawner abundance but seasonal patterns of MDN assimilation were masked in complex habitat where summer MDN assimilation remained high.

Peatland initiation and carbon accumulation in the Falkland Islands

The Falkland Islands in the South Atlantic Ocean contain extensive peatlands at the edge of their global climatic envelope, but the long-term carbon dynamics of these sites is poorly quantified. We present new data for ten sites, compile previously-published data and produce a new synthesis. Many peatlands in the Falkland Islands developed notably early, with a fifth of basal 14C dates pre-Holocene. Falkland Islands peats have high ash content, high carbon content and high bulk density compared to global norms. In many sites carbon accumulation rates are extremely low, which may partly relate to low average rainfall, or to carbon loss through burning and aeolian processes. However, in coastal Tussac peatlands carbon accumulation can be extremely rapid. Our re-analysis of published data from Beauchene Island, the southernmost of the Falkland Islands, yields an exceptional long-term apparent carbon accumulation rate of 139 g C m−2 yr−1, to our knowledge the highest recorded for any global peatland. This high accumulation might relate to the combination of a long growing-season and marine nutrient inputs. Given extensive coverage and carbon-dense peats the carbon stock of Falkland Islands peatlands is clearly considerable but robust quantification will require the development of a reliable peat map. Falkland Island peatlands challenge many standard assumptions and deserve more detailed study.

Indigenous peoples’ habitation history drives present‐day forest biodiversity in British Columbia's coastal temperate rainforest

Abstract Long‐term human habitation has transformed the earth's surface. The combination of time and complex human–environment interactions in remote regions of North America has likely resulted in modified landscapes, though we often consider these regions free of human influence due to the absence of industrial development. We examined long‐term impacts of human resource‐use on British Columbia's coastal rainforest communities. We focused on the region's widespread habitation sites with extensive shell middens to test the legacy of ancient human occupation in present‐day plant communities. Ten habitation sites and 10 control sites in similar locales were selected for floristic surveys and soil sampling. We tested whether plant communities at habitation sites reflected a ‘cultural plant‐use legacy’, with greater presence of culturally significant plant species, and/or a ‘marine nutrient subsidy legacy’ from human use, with increases in species that prefer nutrient‐rich soils. We found that the habitation sites had different plant assemblages than the control sites and were dominated by plants with both higher nutrient requirements and cultural significance. We demonstrate that long‐term occupation has led to strong differences in plant community structure between sites, countering the notion that this is a pristine landscape. We emphasize the value of interdisciplinary approaches and considering past human resource‐use when examining current plant communities. A plain language summary is available for this article.

Stable isotope tracing of links between marine wintering and freshwater breeding habitats of Red-necked Grebes

Stable isotope analyses can detect interactions between different stages of the annual cycle in migratory animals. We used carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) isotopes to identify non-breeding environments, the strategy of nutrient allocation to eggs, and potential carry-over effects from wintering areas in Red-necked Grebes Podiceps grisegena breeding in eastern Poland. Strongly positive isotopic signatures in adult grebe feathers compared to freshwater food webs and feathers of locally fledged young suggested that most adults had moulted in marine areas. Enriched isotopic values in the breast muscles of spring-arriving grebes pointed to transfer of marine-derived nutrients to freshwater breeding sites. Isotopic mixing models revealed that egg nutrients were mainly acquired locally. Endogenous nutrients were to some extent mobilised for the formation of albumen (25–26%, 95% credible interval, three-isotope model) and lipid-free yolk (17–18%, two-isotope, δ13C and δ15N model) in early laid clutches, but were little mobilised, if at all, in clutches of females that delayed laying. The non-breeding trophic feeding level, as indexed by δ15N in feathers of grebe females, was related to laying initiation date (greater enrichment, earlier egg production), indicating cross–seasonal effects on reproduction. Both endogenous nutrient transfer to eggs and a high-quality non-breeding diet may facilitate early breeding, which is advantageous in species constrained by short breeding seasons.

Salmon increase forest bird abundance and diversity.

Resource subsidies across ecosystems can have strong and unforeseen ecological impacts. Marine-derived nutrients from Pacific salmon (Onchorhycus spp.) can be transferred to streams and riparian forests through diverse food web pathways, fertilizing forests and increasing invertebrate abundance, which may in turn affect breeding birds. We quantified the influence of salmon on the abundance and composition of songbird communities across a wide range of salmon-spawning biomass on 14 streams along a remote coastal region of British Columbia, Canada. Point-count data spanning two years were combined with salmon biomass and 13 environmental covariates in riparian forests to test for correlates with bird abundance, foraging guilds, individual species, and avian diversity. We show that bird abundance and diversity increase with salmon biomass and that watershed size and forest composition are less important predictors. This work provides new evidence for the importance of salmon to terrestrial ecosystems and information that can inform ecosystem-based management.

Predation of European catfish on anadromous fish species in an anthropised area

Increases in both food availability and intraspecific competition downstream of dams have the potential to trigger the emergence of trophic specialisation among fish predators, with considerable implications for prey species populations. The aim of this study was to assess whether the presence of a dam located on the River Garonne (France) affected the dietary preference of the European catfish Silurus glanis towards anadromous prey. Stable isotope analysis showed that the contribution of marine-derived carbon in the diet of the European catfish was substantial (on average 53% of the diet) and was similar between individuals caught downstream of the dam and those caught from the free running part of the river. In contrast with previous studies, a significant relationship between the size of European catfish individuals and their consumption of marine-derived nutrients was found in this study. Anadromous fish populations are in decline; therefore, this significant predation is concerning.

Assimilation of marine-derived nutrients from anadromous Rainbow Smelt in an eastern North American riverine food web: evidence from stable-isotope and fatty acid analysis

Movement of anadromous fishes from marine to freshwater habitats provides a seasonal pulse of marine-derived nutrients (MDNs) to freshwater biota. In northeastern North America, iteroparous, anadromous Rainbow Smelt (Osmerus mordax Mitchell, 1814) migrate in high densities to freshwater spawning grounds in early spring. To assess whether 1) MDNs from migratory Rainbow Smelt were incorporated into multiple trophic levels and 2) total fatty acid (FA) compositions of Brook Trout changed during the Rainbow Smelt migration, we compared stable 13C and 15N isotope values and FA profiles of biota in the Pisquid River, Prince Edward Island, Canada. We sampled periphyton, benthic macroinvertebrates, and stream-resident Brook Trout (Salvelinus fontinalis Mitchell, 1814) at a downstream site encompassing Rainbow Smelt spawning grounds and an upstream site inaccessible to Rainbow Smelt. During the Rainbow Smelt migration at the downstream site, predatory caddisflies (Rhyacophilidae) and Brook Trout displayed a 3.1‰ and 1.3‰ increase in δ13C and δ15N, respectively, relative to isotope levels before the migration. Less consistent evidence of MDN assimilation was found in periphyton and nonpredatory macroinvertebrates (Heptageniidae, Elmidae). Increases in δ13C values for Rhyacophilidae and Brook Trout indicated direct consumption of tissue, most probably eggs based on limited stomach content analysis in Brook Trout. FA composition differed between Rainbow Smelt and Brook Trout sampled down- and upstream. Transfer of marine ω-3 FAs was evidenced by statistically similar amounts of eicosapentaenoic and docosahexaenoic acid between Rainbow Smelt and Brook Trout sampled on spawning grounds. We found connections between Rainbow Smelt-based MDNs and stream food webs and a nutritional benefit to Brook Trout.

Seascape connectivity of Gulf sturgeon Acipenser oxyrinchus desotoi population units across the northern Gulf of Mexico

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 37:195-205 (2018) - DOI: https://doi.org/10.3354/esr00923 Seascape connectivity of Gulf sturgeon Acipenser oxyrinchus desotoi population units across the northern Gulf of Mexico Page E. Vick1,*, Mark S. Peterson1, William T. Slack2 1Department of Coastal Science, School of Ocean Science and Engineering, The University of Southern Mississippi, Ocean Springs, MS 39564, USA 2US Army Engineer Research and Development Center, Environmental Laboratory EEA, Vicksburg, MS 39180, USA *Corresponding author: page.vick@noaa.gov ABSTRACT: Critical habitat was designated in 2003 for federally threatened anadromous Gulf sturgeon to aid in population recovery. This study examined overwintering Gulf sturgeon spatial use and movement through critical habitat monitored by the Ship Island acoustic array from 2011 to 2015. Previous studies observed western population Gulf sturgeon (Pearl and Pascagoula rivers) overwintering near the ends and within the passes of the barrier islands of the Mississippi Sound, USA. Recent telemetry studies detected eastern population fish (Escambia, Blackwater, Yellow, and Choctawhatchee rivers) overwintering as far west as Mobile Bay, Alabama; however, this study is the first to observe eastern population fish overwintering in western population critical habitat associated with the Ship Island array. Use of overwintering habitat was compared using mean active days detected and rate of travel to and from the array. There was no significant difference in mean active days of population units on the array; however, travel rate to the array from natal drainages was significantly different, with eastern population individuals traveling at a faster rate compared to western population individuals. Post hoc tests indicated that individuals from the Blackwater River had a significantly higher travel rate compared to Pascagoula River individuals. We documented large-scale seascape connectivity among population units of Gulf sturgeon across the northern Gulf of Mexico. Although large-scale seascape connectivity promotes mixing among population units and an exchange of marine nutrients into riverine environments, large-scale migration poses an issue for endangered species such as Gulf sturgeon, as there is greater risk of bycatch mortality and size-specific predation. KEY WORDS: Acoustic telemetry · Threatened species · Critical overwintering habitat · Migration Full text in pdf format Supplementary material PreviousNextCite this article as: Vick PE, Peterson MS, Slack WT (2018) Seascape connectivity of Gulf sturgeon Acipenser oxyrinchus desotoi population units across the northern Gulf of Mexico. Endang Species Res 37:195-205. https://doi.org/10.3354/esr00923 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 37. Online publication date: October 29, 2018 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2018 Inter-Research.

A multidecade experiment shows that fertilization by salmon carcasses enhanced tree growth in the riparian zone.

As they return to spawn and die in their natal streams, anadromous, semelparous fishes such as Pacific salmon import marine-derived nutrients to otherwise nutrient-poor freshwater and riparian ecosystems. Diverse organisms exploit this resource, and previous studies have indicated that riparian tree growth may be enhanced by such marine-derived nutrients. However, these studies were largely inferential and did not account for all factors affecting tree growth. As an experimental test of the contribution of carcasses to tree growth, for 20yr, we systematically deposited all sockeye salmon (Oncorhynchus nerka) carcasses (217,055 individual salmon) in the riparian zone on one bank of a 2-km-long stream in southwestern Alaska, reducing carcass accumulation on one bank and enhancing it on the other. After accounting for partial consumption and movement of carcasses by brown bears (Ursus arctos) and variation in salmon abundance and body size, we estimated that 267,620kg of salmon were deposited on the enhanced bank and 45,200kg on the depleted bank over the 20yr, for a 5.9-fold difference in total mass. In 2016, we sampled needles of 84 white spruce trees (Picea glauca) the dominant riparian tree species, for foliar nitrogen (N) content and stable isotope ratios (δ15 N), and took core samples for annual growth increments. Stable isotope analysis indicated that marine-derived N was incorporated into the new growth of the trees on the enhanced bank. Analysis of tree cores indicated that in the two decades prior to our enhancement experiment, trees on the south-facing (subsequently the depleted) bank grew faster than those on the north-facing (later enhanced) bank. This difference was reduced significantly during the two decades of fertilization, indicating an effect of the carcass transfer experiment against the background of other factors affecting tree growth.

Enrichment of trace elements in colonies of the yellow-legged gull (Larus michahellis) in the Atlantic Islands National Park (Galicia-NW Spain)

Marine-derived nutrients are known accumulate in seabird breeding colonies due to the deposition of nutrient-rich biological materials, thus greatly altering the functioning and dynamics of these terrestrial ecosystems. Here we present the results of a sampling survey carried out during three years in yellow-legged gull colonies in the Atlantic Islands of Galicia National Park (NW Spain) with the aim of evaluating the influence of the colonies on the accumulation of trace elements, including micronutrients (Cu, Zn, Se, Co, Mo, Ni) and toxic elements (Cr, Cd, Hg, Pb, As, Ag), in the surrounding environments. For this purpose, we analysed samples of biological materials produced by the seabirds (pellets, excrement, feathers, eggs) and of soil, plants and inland water from several different subcolonies and control zones without seabirds.The concentrations of most of the elements were higher in excrement and pellets (mean values: Zn: 152, As: 50 mg kg−1, Cd: 6, Co: 5 mg kg−1) than in feathers and eggs. The flow of trace elements into the breeding colonies, considering only the excrement, revealed a very high level of trace element deposition for a supposedly pristine environment (Zn: 2667, Cd: 70, Cu: 315, As: 64 g ha−1). The total concentrations of trace elements in soil were consistent with the long-term impact of the seabirds. Thus, the values in areas which this impact was greatest were significantly higher than in the control zones, particularly considering the most labile geochemical fractions of the soil. The concentrations of some elements (i.e. Co, As, Cd) were also higher in the inland waters in the colonies than in control zones. Finally, the concentration of trace elements in plants varied depending on the species and element considered.

Breeding eider ducks strongly influence subarctic coastal pond chemistry

Arctic freshwater ponds are typically pristine and oligotrophic, however seabird biovectors can markedly alter water quality via enrichment with marine-derived nutrients and bioaccumulated metals. These ornithogenic inputs can be the dominant factor structuring aquatic biota and the surrounding island flora. Here, we measured a suite of limnological water chemistry variables and sediment geochemistry from 21 freshwater ponds influenced by Common Eiders (Somateria mollissima) in Hudson Strait, near the northern communities of Cape Dorset (Nunavut) and Ivujivik (Quebec). Nest counts and sedimentary δ15N values were used as proxies of bird abundance. Nutrient-rich guano from the nesting eiders visibly promoted the growth of catchment vegetation. Elevated metal (Al, Cd, Zn), metalloid (Se), and nutrient concentrations (N, P) in the water of eider-affected sites were recorded (Sign test; p = 0.004), but the proximity of many sites to the coast meant that variables related to ocean spray (conductivity, Na+, Mg2+, Cl−, Sr) confounded the effects of birds on pond water chemistry. In contrast, sediment geochemistry appeared to more clearly characterize sites according to the level of eider activity in their catchments by tracking Pb, Cd, N, and P sedimentary concentrations (Sign test; p = 0.02). These results have direct implications for reconstructing historical eider population trends using sediment archives, which is necessary to inform effective conservation management strategies.

Modeling Multiple Interacting Nutrient Stocks:Application to the Baltic Sea

Eutrophication of water bodies is a worldwide ecological problem caused by excessive amounts of nutrients. This paper develops an accounting method for modeling multiple interacting stocks of nutrients, which applies the dynamic nutrient balance approach to calculate empirical nutrient budgets. The proposed model of multiple interacting stocks draws an explicit connection between nutrient stocks on land and nutrient stocks in the sea, which in turn links estimated marine nutrient stocks with the empirical data of nutrient concentrations. The model is applied to the Baltic Sea, where stocks of nitrogen and phosphorus are calculated for six basins, drawing distinction between surface, middle and deep water layers of the basins, and taking into account spatial interactions of nutrients within the water layers and between the basins. The model is calibrated using empirical data on nutrient loads and concentrations. Finally, we apply the model to forecast future development of nitrogen and phosphorus concentrations under different abatement scenarios. Keywords: Dynamic Nutrient Model; Multiple Interacting Stocks; Nitrogen; Phosphorus; Eutrophication; Baltic Sea

The Tiny Organisms That Transport Silica Across Earth’s Oceans

Phaeodarians play a major role in marine nutrient cycle.