Nearshore Marine Ecosystems Research Articles

Information Needs Assessment for Coastal and Marine Management and Policy: Ecosystem Services Under Changing Climatic, Land Use, and Demographic Conditions.

Changing climatic, demographic, and land use conditions are projected to alter the provisioning of ecosystem services in estuarine, coastal, and nearshore marine ecosystems, necessitating mitigation and adaptation policies and management. The current paradigm of research efforts occurring in parallel to, rather than in collaboration with, decision makers will be insufficient for the rapid responses required to adapt to and mitigate for projected changing conditions. Here, we suggest a different paradigm: one where research begins by engaging decision makers in the identification of priority data needs (biophysical, economic, and social). This paper uses synthesized interview data to provide insight into the varied demands for scientific research as described by decision makers working on coastal issues in Oregon, USA. The findings highlight the need to recognize (1) the differing framing of ecosystem services by decision makers versus scientists; and (2) the differing data priorities relevant to inland versus coastal decision makers. The findings further serve to highlight the need for decision makers, scientists, and funders to engage in increased communication. This research is an important first step in advancing efforts toward evidence-based decision making in Oregon and provides a template for further research across the US.

Evidence of bottom-up limitations in nearshore marine systems based on otolith proxies of fish growth

Fish otolith growth increments were used as indices of annual production at nine nearshore sites within the Alaska Coastal Current (downwelling region) and California Current (upwelling region) systems (~36–60°N). Black rockfish (Sebastes melanops) and kelp greenling (Hexagrammos decagrammus) were identified as useful indicators in pelagic and benthic nearshore food webs, respectively. To examine the support for bottom-up limitations, common oceanographic indices of production [sea surface temperature (SST), upwelling, and chlorophyll-a concentration] during summer (April–September) were compared to spatial and temporal differences in fish growth using linear mixed models. The relationship between pelagic black rockfish growth and SST was positive in the cooler Alaska Coastal Current and negative in the warmer California Current. These contrasting growth responses to SST among current systems are consistent with the optimal stability window hypothesis in which pelagic production is maximized at intermediate levels of water column stability. Increased growth rates of black rockfish were associated with higher chlorophyll concentrations in the California Current only, but black rockfish growth was unrelated to the upwelling index in either current system. Benthic kelp greenling growth rates were positively associated with warmer temperatures and relaxation of downwelling (upwelling index near zero) in the Alaska Coastal Current, while none of the oceanographic indices were related to their growth in the California Current. Overall, our results are consistent with bottom-up forcing of nearshore marine ecosystems—light and nutrients constrain primary production in pelagic food webs, and temperature constrains benthic food webs.

Broad sampling and diverse biomarkers allow characterization of nearshore particulate organic matter

Suspended particulate organic matter (POM) is a primary food source for benthic and pelagic consumers in aquatic and marine ecosystems. POM is potentially composed of many sources including phytoplankton, bacteria, zooplankton and macrophyte (seaweed and seagrass) and terrestrial detritus. The relative importance of these sources to POM consumers is debated, in large part due to differing interpretations of stable isotope and fatty acid biomarkers. We investigated POM composition in a nearshore marine ecosystem using multiple methods including visual quantification of living and detrital components, multiple stable isotope (MSI) and fatty acid (FA) analyses. Sampling was conducted at multiple temporal and spatial scales to 1) determine the range of variability in POM biomarkers, 2) quantitatively evaluate δ13C, δ15N, δ34S and FA biomarkers with proportional abundance of putative sources and 3) determine the availability of phytoplankton, macrophytes and terrestrial carbon in nearshore POM. Variation of total FA concentration and proportions, and δ13C and δ34S were strongly correlated to phytoplankton abundance, at tidal and seasonal timescales. Using multivariate multiple regressions, MSI and FA explained 59.6% and 89.7% of the variation in POM composition, respectively. As phytoplankton abundance increased, total FA concentration increased concurrent to δ13C and δ34S enrichment. In high detritus samples, bacterial FA and saturated FA were proportionally higher, corresponding to depletion of δ13C and δ34S and enrichment of δ15N. We identify MSI and FA biomarkers that are good predictors of diatom, dinoflagellate and detrital contributions to the POM. The results of this multi‐scale study show that POM composition is highly dynamic and largely driven by phytoplankton abundance, with minor contributions from terrestrial or macrophyte subsidies. This quantitative approach provides novel and critical empirical information linking POM compositional dynamics to specific biomarkers that are commonly used for tracking energy subsidies and biogeochemical cycling in aquatic ecosystems.

A scrutiny of the evidence for pressure-induced state shifts in estuarine and nearshore ecosystems

The concept of nonlinear, sudden responses of ecosystems or species to environmental change has engendered significant interest in the past two decades. Many reviews and theoretical papers have addressed alternative states or stable states, regime shifts, tipping points and phase shifts, but the empirical evidence for these phenomena, which we refer to as stark changes, has not been evaluated in estuaries and nearshore marine ecosystems. We developed standard definitions for these phenomena and examined the functional forms of ecological responses to environmental pressures (i.e. proximate influences on ecosystem state). We searched for publications related to estuaries and nearshore marine ecosystems that included common descriptors of stark change in their keywords. Our search yielded 376 papers, of which we retained 98 that met four criteria: (1) claimed a stepped biological change; (2) inferred change from empirical data; (3) addressed changes that occurred in one or more semi-enclosed, tidally influenced ecosystems; and (4) described a connection to long-term patterns of ecological change. Although there were many instances of changes in ecological states, most were not stark changes. Evidence generally was not derived from time-series data, and many studies inferred temporal change from spatial differences. We describe the eight studies that provided some evidence of stark changes in ecosystem state. We suggest that compelling evidence of stark changes that can be related to pressures requires concurrent time-series data on the ecological response and pressures that were claimed to induce the stark changes.

Key food web technique and evaluation of nearshore marine ecological restoration of Bohai Bay

An ecological key food web restoration technique is proposed to restore the degraded nearshore marine ecosystem near the Bohai Bay, in which the key species are screened and the local key food web is built according to the trophic relationships of screening species to reference ecosystem. The trophic relationships of the key food web are quantified by the biomass of the screening species of each trophic level and the restoration input biomass is fixed. The restoration effect of the proposed technique on the restored ecosystem is predicted by the maturity and health with the Ecopath model and the ocean health index. The proposed technique is applied to the First Harbor of Tianjin Lin Gang Economic Zone. The calculated restoration effect shows that the restored (target) ecosystem is more mature, faster ecological balanced and healthier than the existing ecosystem. The ocean health index of the target ecosystem is 86.3, which is much higher than 51.8 of the existing ecosystem. It is concluded that the proposed technique is effective and applicable in the nearshore marine ecosystem restoration.

Ecosystem functioning impacts of the invasive seaweed Sargassum muticum (Fucales, Phaeophyceae).

Ongoing changes in natural diversity due to anthropogenic activities can alter ecosystem functioning. Particular attention has been given to research on biodiversity loss and how those changes can affect the functioning of ecosystems, and, by extension, human welfare. Few studies, however, have addressed how increased diversity due to establishment of nonindigenous species (NIS) may affect ecosystem function in the recipient communities. Marine algae have a highly important role in sustaining nearshore marine ecosystems and are considered a significant component of marine bioinvasions. Here, we examined the patterns of respiration and light-use efficiency across macroalgal assemblages with different levels of species richness and evenness. Additionally, we compared our results between native and invaded macroalgal assemblages, using the invasive brown macroalga Sargassum muticum (Yendo) Fensholt as a model species. Results showed that the presence of the invader increased the rates of respiration and production, most likely as a result of the high biomass of the invader. This effect disappeared when S.muticum lost most of its biomass after senescence. Moreover, predictability-diversity relationshipsof macroalgal assemblages varied between native and invaded assemblages. Hence, the introduction of high-impact invasive species may trigger major changes in ecosystem functioning. The impact of S.muticum may be related to its greater biomass in the invaded assemblages, although species interactions and seasonality influenced the magnitude of the impact.

Preferences for Management of Near-Shore Marine Ecosystems: A Choice Experiment in New Zealand

There is considerable interest in New Zealand in establishing “Customary Management Areas” (taiāpure and mātaitai) and Marine Reserves to support Māori cultural practices and restore declining biodiversity and fish stocks. Allocation of near-shore marine areas for these management systems potentially benefits the larger public, but it has often been vigorously opposed by recreational and commercial fishers. This paper reports estimates of the relative values held by the public toward four potentially conflicting uses of near-shore marine areas. These estimates come from a web-based choice survey completed by 1055 respondents recruited from throughout New Zealand. The response rate was especially high at 60%. We present results weighted to the characteristics of the population and test the results against a variety of well-known sources of survey bias. Scenario development suggests that some reallocation of near-shore marine areas to any of the management systems under discussion alternative to the status quo is likely to yield a welfare gain. A combination of marine reserves and taiāpure is most preferred. The exercise supports the use of discrete choice experiments to provide crucial information about difficult-to-quantify public values for aspects of management of near-shore marine areas, such as proposed taiāpure, mātaitai, or marine reserves.

Variability of temperature and chlorophyll of the Iberian Peninsula near costal ecosystem during an upwelling event for the present climate and a future climate scenario

Understanding the importance and the implication of the climate changes on coastal areas may be one of the major issues for this and next centuries. Climate changes may, indeed, impact the nearshore marine ecosystem, as coastal areas are very sensitive to the strength and the variability of the meteorological forcings.The main purpose of this work is to study temperature and phytoplankton distributions along the Portuguese near coastal zone during upwelling events in the present climate conditions and in a future climate scenario. The SRES-A2 IPCC scenario has been considered.We have used a three-dimensional model for coastal and shelf seas, including the following sub-models: hydrodynamical/physical, biological, sediment and contaminant. The forcings are provided by the interactions at the air–sea, considering the wind intensity and direction with the help of the WRF model (Weather Research and Forecast Model) and the coupled atmosphere–ocean model ECHAM5/MPI-OM.Results show that, for the future climate scenario, there is a reinforcement of the southward wind. The responses of the coastal ecosystem corresponds to the reinforcement of both, the southward (up to 10cm/s) and the westward (up to 6cm/s) induced upwelling currents. This, in turn generates an enlargement of the near coast upwelled cold layer, extending up to 60km, as well as the rise of the warm layer temperature (up to 2.0°C) and the spreading of the phytoplankton offshore. Significant changes in both the Chl-a vertical and the horizontal distribution patterns have been observed, as the nutrient supply to the upper layers depends on the strength of the upwelling, the bottom topography and orography of the coastal. These results confirm that changes in the strength and eventually the frequency of the upwelling favourable wind impact the phytoplankton distribution, which can have significant effect in the distribution and population of the upper level of the trophic chain of the coastal ecosystem.

A Global Trend towards the Loss of Evolutionarily Unique Species in Mangrove Ecosystems

The mangrove biome stands out as a distinct forest type at the interface between terrestrial, estuarine, and near-shore marine ecosystems. However, mangrove species are increasingly threatened and experiencing range contraction across the globe that requires urgent conservation action. Here, we assess the spatial distribution of mangrove species richness and evolutionary diversity, and evaluate potential predictors of global declines and risk of extinction. We found that human pressure, measured as the number of different uses associated with mangroves, correlated strongly, but negatively, with extinction probability, whereas species ages were the best predictor of global decline, explaining 15% of variation in extinction risk. Although the majority of mangrove species are categorised by the IUCN as Least Concern, our finding that the more threatened species also tend to be those that are more evolutionarily unique is of concern because their extinction would result in a greater loss of phylogenetic diversity. Finally, we identified biogeographic regions that are relatively species-poor but rich in evolutionary history, and suggest these regions deserve greater conservation priority. Our study provides phylogenetic information that is important for developing a unified management plan for mangrove ecosystems worldwide.

Invasion Status of Terrestrial Mammals on Uninhabited Islands within the San Juan Archipelago, Washington

To assess potential impacts of native and invasive terrestrial mammals on near-shore marine ecosystems on islands within the San Juan archipelago, Washington, we surveyed for the presence or non-detection of predatory mammals on a subset of 14 uninhabited islands: 10 that are part of the San Juan Islands National Wildlife Refuge, 3 that are managed by the Bureau of Land Management (BLM), and 1 that is owned by The Nature Conservancy (TNC). We were unable to detect invasive terrestrial mammals on any of the 14 islands. We found native mice (Peromyscus maniculatus) and voles (Microtus townsendi) on one island each, and native raccoons (Procyon lotor pacifica) on three islands. We speculate that the nearly ubiquitous presence of native river otters (Lontra canadensis) along with native predatory birds may be preventing immigrant invasive mammals (primarily house mice [Mus musculus] and rats [Rattus spp.]) from gaining a foot-hold on the islands. Inadequate habitat and/or island size and distance from larger islands and their source populations along with insufficient trap nights may also have contributed to the non-detection of small mammals on the islands we surveyed. For the best chance at keeping these islands free of invaders, we recommend future surveys using continuous measurement methods (e.g., track plates and monitoring blocks) for early detection of future invasions.

Effects of isolation and fishing on the marine ecosystems of Easter Island and Salas y Gómez, Chile

ABSTRACTAn expedition to Salas y Gómez and Easter islands was conducted to develop a comprehensive baseline of the nearshore marine ecosystem, to survey seamounts of the recently created Motu Motiro Hiva Marine Park (MMHMP) – a no‐take marine reserve of 150 000 km2 – and to compare these results with Easter Island where the marine ecosystem is similar but has no marine protection.Live coral cover was surprisingly high at both Easter Island (53%) and Salas y Gómez (44%), especially considering their sub‐tropical location, high wave energy environments, and geographic isolation.Endemic and regionally‐endemic species comprised 77% of the fish abundance at Easter Island and 73% at Salas y Gómez. Fish biomass at Salas y Gómez was relatively high (1.2 t ha‐1) and included a large proportion of apex predators (43%), whereas at Easter Island it was almost three times lower (0.45 t ha‐1) with large predators accounting for less than 2% of the biomass, despite good habitat quality.The large cohort of small sharks and the absence of larger sharks at Salas y Gómez suggest mesopredator release consistent with recent shark fishing. The fish fauna at the seamounts between Easter Island and Salas y Gómez, outside of MMHMP, harboured 46% endemic species, including a new species of damselfish (Chromis sp. nov.) and probably a new species of Chimaera (Hydrolagus). Numerous seamounts adjacent to Salas y Gómez are currently not included in the MMHMP.This expedition highlights the high biodiversity value of this remote part of the Pacific owing to the uniqueness (endemicity) of the fauna, large apex predator biomass, and geographic isolation.Copyright © 2013 John Wiley & Sons, Ltd.

High temporal and spatial variability of dissolved oxygen and pH in a nearshore California kelp forest

Abstract. Predicting consequences of ocean deoxygenation and ocean acidification for nearshore marine ecosystems requires baseline dissolved oxygen (DO) and carbonate chemistry data that are both high-frequency and high-quality. Such data allow accurate assessment of environmental variability and present-day organism exposure regimes. In this study, scales of DO and pH variability were characterized over one year in a nearshore kelp forest ecosystem in the Southern California Bight. DO and pH were strongly, positively correlated, revealing that organisms on this upwelling shelf are not only exposed to low pH but also to low DO. The dominant scale of temporal DO and pH variability occurred on semidiurnal, diurnal and event (days–weeks) time scales. Daily ranges in DO and pH at 7 m water depth (13 mab) could be as large as 220 μmol kg−1 and 0.36 units, respectively. Sources of pH and DO variation include photosynthesis within the kelp forest ecosystem, which can elevate DO and pH by up to 60 μmol kg−1 and 0.1 units over one week following the intrusion of high-density, nutrient-rich water. Accordingly, highly productive macrophyte-based ecosystems could serve as deoxygenation and acidification refugia by acting to elevate DO and pH relative to surrounding waters. DO and pH exhibited greater spatial variation over a 10 m increase in water depth (from 7 to 17 m) than along a 5 km stretch of shelf in a cross-shore or alongshore direction. Over a three-month time period, mean DO and pH at 17 m water depth were 168 μmol kg−1 and 7.87, respectively. These values represent a 35% decrease in mean DO and 37% increase in [H+] relative to near-surface waters. High-frequency variation was also reduced at depth. The mean daily range in DO and pH was 39% and 37% less, respectively, at 17 m water depth relative to 7 m. As a consequence, the exposure history of an organism is largely a function of its depth of occurrence within the kelp forest. With knowledge of local alkalinity conditions and high-frequency temperature, salinity, and pH data, we estimated pCO2 and calcium carbonate saturation states with respect to calcite and aragonite (Ωcalc and Ωarag) for the La Jolla kelp forest at 7 m and 17 m water depth. pCO2 ranged from 246 to 1016 μatm, Ωcalc was always supersaturated, and Ωarag was undersaturated at the beginning of March for five days when pH was less than 7.75 and DO was less than 115 μmol kg−1. These findings raise the possibility that the benthic communities along eastern boundary current systems are currently acclimatized and adapted to natural, variable, and low DO and pH. Still, future exposure of coastal California populations to even lower DO and pH may increase as upwelling intensifies and hypoxic boundaries shoal, compressing habitats and challenging the physiological capacity of intolerant species.

Genetic Diversity Enhances Restoration Success by Augmenting Ecosystem Services

Disturbance and habitat destruction due to human activities is a pervasive problem in near-shore marine ecosystems, and restoration is often used to mitigate losses. A common metric used to evaluate the success of restoration is the return of ecosystem services. Previous research has shown that biodiversity, including genetic diversity, is positively associated with the provision of ecosystem services. We conducted a restoration experiment using sources, techniques, and sites similar to actual large-scale seagrass restoration projects and demonstrated that a small increase in genetic diversity enhanced ecosystem services (invertebrate habitat, increased primary productivity, and nutrient retention). In our experiment, plots with elevated genetic diversity had plants that survived longer, increased in density more quickly, and provided more ecosystem services (invertebrate habitat, increased primary productivity, and nutrient retention). We used the number of alleles per locus as a measure of genetic diversity, which, unlike clonal diversity used in earlier research, can be applied to any organism. Additionally, unlike previous studies where positive impacts of diversity occurred only after a large disturbance, this study assessed the importance of diversity in response to potential environmental stresses (high temperature, low light) along a water–depth gradient. We found a positive impact of diversity along the entire depth gradient. Taken together, these results suggest that ecosystem restoration will significantly benefit from obtaining sources (transplants or seeds) with high genetic diversity and from restoration techniques that can maintain that genetic diversity.

Kelp Bed Dynamics in Estuarine Environments in Subarctic Alaska

Abstract Glaciers have pronounced long- and short-term effects on nearshore marine ecosystems. Concerns exist about possible changes that may occur to nearshore habitats with the pronounced climatic alterations in subarctic and high-latitude environments. The present research studied the effects of glacial discharge on kelp bed community structure by comparing environmental conditions on one more exposed and one less exposed shore in a subarctic Alaskan estuary. Inorganic sedimentation, abrasion, and percent sand/silt substrate were significantly higher on the more exposed shore than the less exposed shore. Light intensity, salinity, nitrate concentrations, and hard substrate cover were significantly lower on the more exposed shore. Kelp bed communities on the more exposed shore contained only one kelp species, Saccharina latissima, versus five kelp species on the less exposed shore. Taxonomic richness and overall organism abundance were significantly lower on the more exposed shore. Salinity, nitrate, in...

Identifying critical regions in small-world marine metapopulations

The precarious state of many nearshore marine ecosystems has prompted the use of marine protected areas as a tool for management and conservation. However, there remains substantial debate over their design and, in particular, how to best account for the spatial dynamics of nearshore marine species. Many commercially important nearshore marine species are sedentary as adults, with limited home ranges. It is as larvae that they disperse greater distances, traveling with ocean currents sometimes hundreds of kilometers. As a result, these species exist in spatially complex systems of connected subpopulations. Here, we explicitly account for the mutual dependence of subpopulations and approach protected area design in terms of network robustness. Our goal is to characterize the topology of nearshore metapopulation networks and their response to perturbation, and to identify critical subpopulations whose protection would reduce the risk for stock collapse. We define metapopulation networks using realistic estimates of larval dispersal generated from ocean circulation simulations and spatially explicit metapopulation models, and we then explore their robustness using node-removal simulation experiments. Nearshore metapopulations show small-world network properties, and we identify a set of highly connected hub subpopulations whose removal maximally disrupts the metapopulation network. Protecting these subpopulations reduces the risk for systemic failure and stock collapse. Our focus on catastrophe avoidance provides a unique perspective for spatial marine planning and the design of marine protected areas.

Marine fisheries declines viewed upside down: human impacts on consumer-driven nutrient recycling

We quantified how two human impacts (overfishing and habitat fragmentation) in nearshore marine ecosystems may affect ecosystem function by altering the role of fish as nutrient vectors. We empirically quantified size-specific excretion rates of one of the most abundant fishes (gray snapper, Lutjanus griseus) in The Bahamas and combined these with surveys of fish abundance to estimate population-level excretion rates. The study was conducted across gradients of two human disturbances: overfishing and ecosystem fragmentation (estuaries bisected by roads), to evaluate how each could result in reduced population-level nutrient cycling by consumers. Mean estimated N and P excretion rates for gray snapper populations were on average 456% and 541% higher, respectively, in unfished sites. Ecosystem fragmentation resulted in significant reductions of recycling rates by snapper, with degree of creek fragmentation explaining 86% and 72% of the variance in estimated excretion for dissolved N and P, respectively. Additionally, we used nutrient limitation assays and primary producer nutrient content to provide a simple example of how marine fishery declines may affect primary production. This study provides an initial step toward integrating marine fishery declines and consumer-driven nutrient recycling to more fully understand the implications of human impacts in marine ecosystems.

The impact of glacier runoff on the biodegradability and biochemical composition of terrigenous dissolved organic matter in near-shore marine ecosystems

The processing of terrigenous dissolved organic matter (DOM) by aquatic food webs modifies its biochemical composition from riverine to coastal ecosystems. We used parallel factor analysis (PARAFAC) of fluorescence excitation–emission matrices (EEMs) and biodegradable dissolved organic carbon (BDOC) incubations to investigate changes in the biochemical composition and lability of terrigenous DOM in three estuaries of coastal southeastern Alaska: 1) a watershed with high glacial coverage, 2) low glacial coverage, and 3) low glacial coverage and high wetland coverage. Laboratory BDOC incubations were conducted for each site by inoculating filtered river water with microbial inocula collected from four different salinities (0, 2, 10 and 25) along the estuarine transect. The percent BDOC for all three sites ranged from 22 to 44% for the 28-day incubations and was greatest in the estuary draining the highly glaciated watershed. Moreover, percent BDOC was greatest for river water samples inoculated with marine compared to freshwater bacteria suggesting marine bacterioplankton were able to utilize a larger fraction of the terrigenous DOM pool than riverine microbes. PARAFAC modeling of fluorescence EEMs showed non-conservative estuarine mixing behavior for DOM including removal at low salinities and addition at mid-high salinities for all three sites. For example, tyrosine-like fluorescence decreased dramatically between salinity values 0 and 0.5 and was undetectable by salinity 2 for all three estuaries. However, humic-like C4 (correlated with aliphatic carbon content) and tryptophan-like fluorescence increased non-conservatively during estuarine mixing, likely associated with an increase in bacterioplankton growth. These results indicate that terrigenous DOM, particularly from glacial runoff, is an important source of carbon and nutrients to near-shore coastal zones of southeast Alaska.

Biological consequences of organic pollution of nearshore marine ecosystems in the Russian waters of the Sea of Japan

The process of the inflow and accumulation of organic matter in the bays and bights of the Russian coast of the Sea of Japan was evaluated. Changes in the composition and structure of marine communities that take place in certain water bodies of Primorsky Krai were shown using the author’s own material and literature data. The rating of water bodies by the degree of the anthropogenic transformation of biocenoses as a result of the accumulation of organic matter was performed.

Mollusks and Mass Harvesting in the Middle Holocene

Archaeological excavations at California Channel Island sites have produced a history of roughly 12,000 years of maritime subsistence, technological change, human-environmental interactions, and cultural evolution. These excavations provide valuable data on the dynamics of Channel Island nearshore marine ecosystems and the adaptive strategies of maritime hunter-gatherers who foraged, fished, and hunted in them for millennia. In this article, we summarize the context, chronology, and implications of two Middle Holocene sites on San Miguel Island, where black turban snails (<i>Tegula funebralis</i>) dominate the faunal assemblages. We discuss the dominance of small shellfish in relation to optimal foraging theory and the general belief that larger-bodied animals were more attractive to ancient coastal foragers.

Effects of changing glacial coverage on the physical and biogeochemical properties of coastal streams in southeastern Alaska

Runoff from mountain glaciers and icecaps is a critical control on physical and chemical conditions of aquatic ecosystems in glaciated watersheds. To date, there has been little research on the biogeochemistry of proglacial streams. Here we use a space for time substitution to evaluate how stream water physical conditions and concentrations of carbon, nitrogen, and phosphorus may be altered by diminishing glacial coverage. For a full annual hydrograph, we sampled six watersheds in southeastern Alaska that ranged in glacier coverage from 0 to 55%. We found that during the summer runoff season (May–October), stream water temperature and specific conductivity were negatively correlated with the percentage of the watershed covered by glacial ice, while stream water turbidity showed a significant positive correlation. Stream water concentrations of dissolved organic carbon (DOC) were typically low (0.5–3.0 mg C L−1) and showed a significant trend toward higher concentrations as watershed glacier coverage decreased. Concentrations of dissolved organic nitrogen (DON) and dissolved inorganic nitrogen also increased significantly with decreasing glacial coverage. In contrast, concentrations of soluble reactive phosphorus decreased with lower glacial coverage. Interestingly, we found that the DOC:DON ratio of stream water dissolved organic matter (DOM) decreased with increasing glacier coverage, suggesting that glaciers may be a source of N‐rich DOM. During winter low flows (November–April) there were few differences in stream water physical and biogeochemical conditions across the six watersheds as glacial inputs diminished and streamflow was dominated by groundwater. Our findings suggest that in southeastern Alaska ongoing glacial recession and the associated land cover change will impact physical and biogeochemical conditions in coastal streams, with implications for salmon spawning habitat, aquatic ecosystem productivity, and fluxes of reactive nutrients to downstream nearshore marine ecosystems.