A primary focus of coastal science during the past 3 decades has been the question: How does anthropogenic nutrient enrichment cause change in the structure or function of nearshore coastal ecosystems? This theme of environmental science is recent, so our conceptual model of the coastal eutrophication problem continues to change rapidly In this review, I suggest that the early (Phase I) con- ceptual model was strongly influenced by limnologists, who began intense study of lake eutrophication by the 1960s The Phase I model emphasized changing nutrient input as a signal, and responses to that signal as increased phytoplankton biomass and primary production, decomposition of phytoplankton- derived organic matter, and enhanced depletion of oxygen from bottom waters Coastal research in recent decades has identified key differences in the responses of lakes and coastal-estuarine ecosystems to nutrient enrichment The contemporary (Phase II) conceptual model reflects those differences and includes explicit recognition of (1) system-specific attributes that act as a filter to modulate the responses to enrichment (leading to large differences among estuarine-coastal systems in their sensitivity to nu- trient enrichment); and (2) a complex suite of direct and indirect responses including linked changes in: water transparency, distribution of vascular plants and biomass of macroalgae, sediment biogeochem- istry and nutrient cycling, nutrient ratios and their regulation of phytoplankton community composition, frequency of toxic/harmful algal blooms, habitat quality for metazoans, reproduction/growth/survival of pelagic and benthic invertebrates, and subtle changes such as shifts in the seasonality of ecosystem functions Each aspect of the Phase II model is illustrated here with examples from coastal ecosystems around the world In the last section of this review I present one vision of the next (Phase III) stage in the evolution of our conceptual model, organized around 5 questions that will guide coastal science in the early 21st century: (1) How do system-specific attributes constrain or amplify the responses of coastal ecosystems to nutrient enrichment? (2) How does nutrient enrichment interact with other stressors (toxic contaminants, fishing harvest, aquaculture, nonindigenous species, habitat loss, climate change, hydro- logic manipulations) to change coastal ecosystems? (3) How are responses to multiple stressors linked? (4) How does human-induced change in the coastal zone impact the Earth system as habitat for humanity and other species? (5) How can a deeper scientific understanding of the coastal eutrophication problem be applied to develop tools for building strategies at ecosystem restoration or rehabilitation?

https://www.int-res.com/articles/meps/210/m210p223.pdf

Our evolving conceptual model of the coastal eutrophication problem

The rise of harmful cyanobacteria blooms: The potential roles of eutrophication and climate change

Climate change: links to global expansion of harmful cyanobacteria.

Marine dissolved organic matter (DOM) is a complex mixture of molecules found throughout the world's oceans. It plays a key role in the export, distribution, and sequestration of carbon in the oceanic water column, posited to be a source of atmospheric climate regulation. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, focuses on the chemical constituents of DOM and its biogeochemical, biological, and ecological significance in the global ocean, and provides a single, unique source for the references, information, and informed judgments of the community of marine biogeochemists. Presented by some of the world's leading scientists, this revised edition reports on the major advances in this area and includes new chapters covering the role of DOM in ancient ocean carbon cycles, the long term stability of marine DOM, the biophysical dynamics of DOM, fluvial DOM qualities and fate, and the Mediterranean Sea. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, is an extremely useful resource that helps people interested in the largest pool of active carbon on the planet (DOC) get a firm grounding on the general paradigms and many of the relevant references on this topic. * Features up-to-date knowledge of DOM, including five new chapters* The only published work to synthesize recent research on dissolved organic carbon in the Mediterranean Sea* Includes chapters that address inputs from freshwater terrestrial DOM

Biogeochemistry of marine dissolved organic matter

Background: Recent declines in honey bees for crop pollination threaten fruit, nut, vegetable and seed production in the United States. A broad survey of pesticide residues was conducted on samples from migratory and other beekeepers across 23 states, one Canadian province and several agricultural cropping systems during the 2007–08 growing seasons. Methodology/Principal Findings: We have used LC/MS-MS and GC/MS to analyze bees and hive matrices for pesticide residues utilizing a modified QuEChERS method. We have found 121 different pesticides and metabolites within 887 wax, pollen, bee and associated hive samples. Almost 60% of the 259 wax and 350 pollen samples contained at least one systemic pesticide, and over 47% had both in-hive acaricides fluvalinate and coumaphos, and chlorothalonil, a widely-used fungicide. In bee pollen were found chlorothalonil at levels up to 99 ppm and the insecticides aldicarb, carbaryl, chlorpyrifos and imidacloprid, fungicides boscalid, captan and myclobutanil, and herbicide pendimethalin at 1 ppm levels. Almost all comb and foundation wax samples (98%) were contaminated with up to 204 and 94 ppm, respectively, of fluvalinate and coumaphos, and lower amounts of amitraz degradates and chlorothalonil, with an average of 6 pesticide detections per sample and a high of 39. There were fewer pesticides found in adults and brood except for those linked with bee kills by permethrin (20 ppm) and fipronil (3.1 ppm). Conclusions/Significance: The 98 pesticides and metabolites detected in mixtures up to 214 ppm in bee pollen alone represents a remarkably high level for toxicants in the brood and adult food of this primary pollinator. This represents over half of the maximum individual pesticide incidences ever reported for apiaries. While exposure to many of these neurotoxicants elicits acute and sublethal reductions in honey bee fitness, the effects of these materials in combinations and their direct association with CCD or declining bee health remains to be determined.

/pdf/high-levels-of-miticides-and-agrochemicals-in-north-american-2xshly0auh.pdf

High levels of miticides and agrochemicals in North American apiaries: implications for honey bee health.

Massive summer blooms of nitrogen-fixing cyanobacteria have been documented in the Baltic Sea since the 19th century, but are reported to have increased in frequency, biomass, and duration in recen 

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2000.45.3.0716

Cyanobacterial blooms in the Baltic Sea: Natural or human-induced?

Unprecedented agricultural intensification and increased crop yield will be necessary to feed the burgeoning world population, whose global food demand is projected to double in the next 50 years. Although grain production has doubled in the past four decades, largely because of the widespread use of synthetic nitrogenous fertilizers, pesticides, and irrigation promoted by the "Green Revolution," this rate of increased agricultural output is unsustainable because of declining crop yields and environmental impacts of modern agricultural practices. The last 20 years have seen diminishing returns in crop yield in response to increased application of fertilizers, which cannot be completely explained by current ecological models. A common strategy to reduce dependence on nitrogenous fertilizers is the production of leguminous crops, which fix atmospheric nitrogen via symbiosis with nitrogen-fixing rhizobia bacteria, in rotation with nonleguminous crops. Here we show previously undescribed in vivo evidence that a subset of organochlorine pesticides, agrichemicals, and environmental contaminants induces a symbiotic phenotype of inhibited or delayed recruitment of rhizobia bacteria to host plant roots, fewer root nodules produced, lower rates of nitrogenase activity, and a reduction in overall plant yield at time of harvest. The environmental consequences of synthetic chemicals compromising symbiotic nitrogen fixation are increased dependence on synthetic nitrogenous fertilizer, reduced soil fertility, and unsustainable long-term crop yields.

https://www.pnas.org/content/pnas/104/24/10282.full.pdf

Pesticides reduce symbiotic efficiency of nitrogen-fixing rhizobia and host plants

Mechanisms of ammonia and amino acid photoproduction from aquatic humic and colloidal matter.

Long-term (1977–2000) ecological biomass data for total phytoplankton, diatoms, and cyanobacteria, based on plankton samples from Himmerfjarden Bay (Baltic proper), were compared to the historical sediment record using diagnostic plant pigment biomarkers. Radionuclides (210Pb and 137Cs) were used to determine chronology, sedimentation, and carbon burial rate. Despite high resolution sampling, using crust-freeze sampling, of sediment layers representing annual varves, no significant correlations between pigments preserved in sediments and phytoplankton biomass in plankton samples were detected for periods of 1–4 yr. This lack of correspondence was probably at least partly due to the importance of resuspension events in Himmerfjarden. When sedimentary pigments were averaged over longer time intervals (5 yr) averages of annual diatom biomass in the Himmerfjard inlet were positively correlated to down-core concentrations of fucoxanthin (r2 = 0.98) and diatoxanthin (r2 = 0.62). This indicates that pigment biomarkers can still be used to interpret longer term development of eutrophication-related blooms in such estuarine systems. In contrast, zeaxanthin concentrations were not significantly correlated (p > 0.05, r2 = 0.05) to cyanobacterial biomass as a 5–yr average. Using fossil pigments to determine relative differences in phytoplankton biomass composition in the absence of historical ecological patterns of phytoplankton composition can be misleading due to selective losses of pigments such as the epoxy-carotenoids. However, while the use of fossil pigments in laminated sediments alone may not allow for detailed interpretations of past phytoplankton communities, it does allow for the simple determination of the presence of significant biomass of phytoplankton classes, for which unique biomarker pigments exist.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2002.47.5.1537

Do sediments from coastal sites accurately reflect time trends in water column phytoplankton? A test from Himmerfjärden Bay (Baltic Sea proper)

The composition and cycling of high-molecular-weight dissolved organic carbon (HMW-DOC) were examined in a tidal stream (Bayou Trepagnier) with seasonally high DOC concentrations (1.0‐5.6 mM). 13 C nuclear magnetic resonance ( 13 C NMR) was used to examine the bulk chemical composition of natural HMW-DOC from two field sites over 1.5 yr. The HMW-DOC at both sites was dominated by aliphatic (41%), carbohydrate (33%), and carboxyl (16%) carbon, with relatively low aromatic carbon abundance (10%). A comparison of 13 C NMR signatures of bayou HMW-DOC and leachate HMW-DOC collected from leaf litter and soils revealed that plant litter leachate appears to be a more important source of HMW-DOM than soil. Dominant sources of HMW-DOC were likely allochthonous inputs of terrestrial plant litter with periodic inputs of soil organic matter during flooding events. The low aromaticity of bayou HMW-DOC may reflect the influence of low-oxygen conditions, which inhibit the decomposition of particulate aromatic macromolecules such as lignin and humic material to HMW-DOC. Ligninphenol biomarker concentrations (L6, in mg/ 100 mg OC) were much lower in HMW-DOC (1.2) than in plant (5.2) and soil (6.8) organic matter, indicating that a significant fraction of this highly aromatic material was not degraded to HMW-DOC. Finally, this study demonstrated that lignin and other compounds from terrestrially derived organic matter in sediments and adjacent soils are not a significant source of more soluble moieties that enter the HMWDOC pool of the bayou. In both freshwater and marine systems, a significant fraction of total dissolved organic carbon (DOC) is composed of high-molecular-weight DOC (HMW-DOC) or colloidal organic carbon. The composition of HMW-DOC is important to nutrient cycling and aquatic chemistry, because this fraction contains substantial amounts of potential bacterial substrates and influences physicochemical characteristics through light attenuation, pH buffering, and metal complexation (McKnight et al. 1994; Battin 1998). Despite the abundance of HMW-DOC in inland waters, most studies advancing our understanding of HMW-DOC cycling have been conducted in the open ocean or large estuaries. In those systems, HMW-DOC appears to be derived mainly from direct exudation by phytoplankton and is rich in polysaccharides, pigments, lipids, and nucleic acids (Bianchi et al. 1995; Biddanda and Benner 1997). In freshwater systems, humic substances derived from diagenesis of structural materials from soils and higher plants are also important contributors to HMW-DOC (Frimmel and Christman 1988; Gustafsson and Gschwend 1997). Relatively little is known about HMW-DOC cycling in coastal wetlands, although wetlands have high DOC concentrations and could be important HMW-DOC sources to es1 Corresponding author.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2001.46.4.0917

Erika Engelhaupt

Papers

Cyanobacterial blooms in the Baltic Sea: Natural or human-induced?

Pesticides reduce symbiotic efficiency of nitrogen-fixing rhizobia and host plants

Mechanisms of ammonia and amino acid photoproduction from aquatic humic and colloidal matter.

Do sediments from coastal sites accurately reflect time trends in water column phytoplankton? A test from Himmerfjärden Bay (Baltic Sea proper)

Sources and composition of high-molecular-weight dissolved organic carbon in a southern Louisiana tidal stream (Bayou Trepagnier)