Nearshore Ecosystems Research Articles

Using a small, consumer grade drone to identify and count marine megafauna in shallow habitats

Large-bodied animals, megafauna, are disproportionately threatened and yet, remain relatively difficult to monitor, particularly true in the ocean. Consumer-grade drones have high definition imagery and offer a non-invasive way to monitor a subset of marine megafauna, especially those species that spend part of their life near the water’s surface. However, a key question is the extent to which drone imagery data offer reliable abundance estimates due to potential detection restraints, and the ability to compare data from different locations. Here we tested the efficacy of a quadcopter drone to collect megafauna abundance data in multiple shallow-water habitats in the realistic background variation of shoreline development. On Great Abaco Island, The Bahamas we repeated drone surveys in nearshore habitats from June to August 2015 at three paired high and low human population sites. We tested the drone's detection probability using decoy organisms and found no effect of water quality or benthic characteristics on detectability. In short, the drones appear to work to monitor these species. We also noted patterns in the occupancy of the species on which we focused. We observed three shark, two ray, and two sea turtle species, finding higher abundances of all species in our low human population sites compared to high human population sites. Our results highlight the ability of consumer-grade drones to estimate the abundance and distribution of large-bodied elasmobranchs and sea turtles in shallow water habitats. Further, our study supports their capability to evaluate issues related to the conservation and management of nearshore ecosystems.

The importance of kelp to an intertidal ecosystem varies by trophic level: insights from amino acid δ13C analysis

AbstractA fundamental question in ecology is understanding how energy and nutrients move through and between food webs, and which sources of production support consumers. In marine ecosystems, these basic questions have been challenging to answer given the limitation of observational methods. Stable isotope analysis of essential amino acids (EAA δ13C) has great potential as a tool to quantify energy and nutrient flow through marine food webs; however, it has been primarily utilized at large spatial scales. Here, we used EAA δ13C analysis to test for connectivity between adjacent subtidal and intertidal components of a nearshore ecosystem in south central Alaska. We measured δ13C of six EAA from four marine producer groups: subtidal kelp (Laminaria sp.), offshore particulate organic matter (POM), and intertidal red (Neorhodomela sp.) and green (Ulva sp.) algae. In addition, we sampled four intertidal invertebrate consumer species spanning a range of trophic/functional groups: Mytilus sp., Strongylocentrotus droebachiensis, Nucella sp., and Pycnopodia helianthoides. Using canonical analysis of principal coordinates (CAP) and isotope mixing models (MixSIAR), we tested for differences among producer EAA δ13C fingerprints and quantified the contribution of producer EAA to consumers. We compared these results to previously published EAA δ13C data on marine producers to examine the generality of this technique. We found the EAA δ13C fingerprints of subtidal kelps (Laminaria), Ulva, and Neorhodomela were highly distinct from one another. Further, our measured EAA δ13C patterns for kelp and red algae matched those previously reported from other localities, suggesting unique and universal EAA δ13C signatures for these groups. However, CAP could not distinguish between microalgae (POM) and Ulva, possibly due to similar biochemical pathways for the synthesis of EAA. Using these producer fingerprints, we found upper trophic‐level invertebrate consumers, Nucella and Pycnopodia, derived more than 60% of their essential amino acids from subtidal kelps. In contrast, the sampled primary consumers in the system, Mytilus and Strongylocentrotus, relied more heavily on Ulva and/or offshore POM. Our results provide evidence for connectivity between two adjacent nearshore ecosystems and exemplify EAA δ13C as a powerful new tool in tracing energy and nutrient flow within and among marine food webs.

Artificial structures as a source of elevated detrital loads for sedimentary environments

Artificial structures, such as seawalls and breakwaters, are essential components of shoreline protection, yet they can have major consequences for marine organisms, particularly those in surrounding sediments. Improved understanding of the mechanisms by which artificial structures influence sedimentary habitats and the scale at which these mechanisms operate is needed to assess impacts of intensifying shoreline armoring on nearshore ecosystems. We examined detrital production on artificial structures and influx into surrounding sedimentary habitat in Puget Sound, Washington. Benthic surveys of hard substrates and drift composition indicated that red macroalgae and encrusting invertebrates were the major producers of detrital material on subtidal artificial structures in the region. Core samples collected at three distances (1, 7, and 15 m) from selected artificial structures revealed that these materials were moving into adjacent sedimentary seascapes and becoming incorporated into the upper layers of sediment. Though detrital influx occurred only in the immediate vicinity of artificial structures, it altered sediment characteristics considerably, increasing the quantity of shell fragments and thus the average grain size, as well as the concentration of red macroalgal detritus in sediments. Furthermore, rapid turnover rates of macroalgal detritus in experimental sediment plots suggested the influx of red macroalgal material from artificial structures was a frequent occurrence. These results indicate that elevated detrital influx is a persistent process in habitats bordering artificial structures in Puget Sound. Further work is needed to assess ecosystem response to detrital influx and to understand detritus-related impacts of shoreline armoring at the landscape scale.

Why less complexity produces better forecasts: an independent data evaluation of kelp habitat models

Understanding how species are distributed in the environment is increasingly important for natural resource management, particularly for keystone and habitat – forming species, and those of conservation concern. Habitat suitability models are fundamental to developing this understanding; however their use in management continues to be limited due to often‐vague model objectives and inadequate evaluation methods. Along the Northeast Pacific coast, canopy kelps (Macrocystis pyrifera and Nereocystis luetkeana) provide biogenic habitat and considerable primary production to nearshore ecosystems. We investigated the distribution of these species by examining a series of increasingly complex habitat suitability models ranging from process‐based models based on species’ ecology to complex generalised additive models applied to purpose‐collected survey data. Seeking empirical limits to model complexity, we explored the relationship between model complexity and forecast skill, measured using both cross‐validation and independent data evaluation. Our analysis confirmed the importance of predictors used in models of coastal kelp distributions developed elsewhere (i.e. depth, bottom type, bottom slope, and exposure); it also identified additional important factors including salinity, and potential interactions between exposure and salinity, and slope and tidal energy. Comparative results showed how cross‐validation can lead to over‐fitting, while independent data evaluation clearly identified the appropriate model complexity for generating habitat forecasts. Our results also illustrate that, depending on the evaluation data, predictions from simpler models can out‐perform those from more complex models. Collectively, the insights from evaluating multiple models with multiple data sets contribute to the holistic assessment of model forecast skill. The continued development of methods and metrics for evaluating model forecasts with independent data, and the explicit consideration of model objectives and assumptions, promise to increase the utility of model forecasts to decision makers.

Habitat effects of macrophytes and shell on carbonate chemistry and juvenile clam recruitment, survival, and growth

Adverse habitat conditions associated with reduced seawater pH often, but not always, negatively affect bivalves in early life history phases. Improving our understanding of how habitat-specific parameters affect clam recruitment, survival, and growth could assist natural resource managers and researchers in developing appropriate adaptation strategies for increasingly acidified nearshore ecosystems. Two proposed adaptation strategies, the presence of macrophytes and addition of shell hash, have the potential to raise local seawater pH and aragonite saturation state and, therefore, to improve conditions for shell-forming organisms. This field study examined the effects of these two substrate treatments on biological and geochemical response variables. Specifically, we measured (1) recruitment, survival, and growth of juvenile clams (Ruditapes philippinarum) and (2) local water chemistry at Fidalgo Bay and Skokomish Delta, Washington, USA, in response to experimental manipulations. Results showed no effect of macrophyte or shell hash treatment on recruitment or survival of R. philippinarum. Contrary to expectations, clam growth was significantly greater in the absence of macrophytes, regardless of the presence or absence of shell hash. Water column pH was higher outside the macrophyte bed than inside at Skokomish Delta and higher during the day than at night at Fidalgo Bay. Additionally, pore-water pH and aragonite saturation state were higher in the absence of macrophytes and the presence of shell. Based on these results, we propose that with increasingly corrosive conditions shell hash may help provide chemical refugia under future ocean conditions. Thus, we suggest adaptation strategies target the use of shell hash and avoidance of macrophytes to improve carbonate chemistry conditions and promote clam recruitment, survival, and growth.

Resilience of Atlantic Slippersnail Crepidula fornicata Larvae in the Face of Severe Coastal Acidification

Globally, average oceanic pH is dropping, and it will continue to decline into the foreseeable future. This ocean acidification (OA) will exacerbate the natural fluctuations in pH that nearshore ecosystems currently experience daily, potentially pushing marine organisms to their physiological limits. Adults of Crepidula fornicata (the Atlantic slippersnail) have proven remarkably resilient to many environmental changes, which is perhaps not surprising considering that they are common intertidally, have a geographically large native range, and have been extremely successful at invading coastal water in many other parts of the world. However, the larvae of C. fornicata have been shown to be somewhat more vulnerable than adults to the effects of reduced pH. Research to date has focused on the physiological impacts of OA on C. fornicata larvae; few studies have explored shifts in gene expression resulting from changes in pH. In the present study, we examined the response of young (4-day old) C. fornicata larvae to two extreme OA treatments (pH 7.5 and 7.6) relative to pH 8.0, documenting both phenotypic and genome-wide gene expression responses. We found that rearing larvae at reduced pH had subtle influences on gene expression, predominantly involving downregulation of genes related to growth and metabolism, accompanied by significantly reduced shell growth rates only for larvae reared at pH 7.5. Additionally, 10-day old larvae that had been reared at the two lower pH levels were far less likely to metamorphose within six hours when exposed to inducer. However, all larvae eventually reached similarly high levels of metamorphosis 24 hours after settlement induction. Finally, there were no observed impacts of OA on larval mortality. Taken together, our results indicate that far future OA levels have observable, but not severe, impacts on C. fornicata larvae, which is consistent with the resilience of this invasive snail across rapidly changing nearshore ecosystems. We propose that future work should delve further into the physiological and transcriptomic responses of all life history stages to gain a more comprehensive understanding of how OA impacts the littoral gastropod C. fornicata.

Functional diversity responses of a nearshore fish community to restoration driven by large-scale dam removal

Large scale dams have numerous significant impacts on river and nearshore components of watersheds. Large scale dam removal is therefore an increasingly useful restoration tool that reestablishes physical processes and habitats that form nearshore ecosystems. Removing large scale dams will likely affect the functional ecology of nearshore ecosystems, but this concept has yet to be explored. Here we use data from a decade long study to define how the functional ecology of fish responded to large scale dam removal. Dam removal resulted in shifts in the nearshore through the reconnection of riverine and marine hydrodynamic system, large-scale and rapid creation of nearshore habitats, and a shift in nearshore habitats from tidally influenced to non-tidally influenced habitats. The functional diversity of the fish community within the system restored by dam removal was volatile during and after dam removal. Dam removal released sediment that formed new lower river and estuary. These new nearshore habitats supported a fish community of significantly greater functional dispersion and entropy relative to previously present beaches within and outside the new delta. That is, species unique in their diet, habitat use, morphology, and size were abundant relative to less functionally unique fish in newly formed beaches. These trends were temporary as there were no significant differences in functional diversity or entropy of fishes among sites after the restoration. Newly formed habitats proved to be more diverse but had lower resiliency after dam removal. Newly establishing nearshore sites appear more vulnerable to non-native and nuisance species that could disrupt the establishment of the watershed and shoreline. While functional richness at the original estuary sites dropped dramatically after dam removal, resiliency was higher after dam removal corresponding to a shift from estuary to lower river side channel habitat, indicating a more stable nearshore zone than new sites. We anticipate that functional diversity at the newly formed nearshore areas will stabilize as the habitats are vegetated and mature.

Differential sensitivity of larvae to ocean acidification in two interacting mollusc species

Anthropogenically-induced ocean acidification (OA) scenarios of decreased pH and altered carbonate chemistry are threatening the fitness of coastal species and hence near-shore ecosystems' biodiversity. Differential tolerances to OA between species at different trophic levels, for example, may alter species interactions and impact community stability. Here we evaluate the effect of OA on the larval stages of the rock oyster, Saccostrea cucullata, a dominant Indo-Pacific ecosystem engineer, and its key predator, the whelk, Reishia clavigera. pH as low as 7.4 had no significant effect on mortality, abnormality or growth of oyster larvae, whereas whelk larvae exposed to pH 7.4 experienced increased mortality (up to ∼30%), abnormalities (up to 60%) and ∼3 times higher metabolic rates compared to controls. Although these impacts' long-term consequences are yet to be investigated, greater vulnerability of whelk larvae to OA could impact predation rates on intertidal rocky shores, and have implications for subsequent community dynamics.

Temporal Variability in Ecological Stoichiometry and Material Exchange in a Tidally Dominated Estuary (North Inlet, South Carolina) and the Impact on Community Nutrient Status

Across the coastal zone, rates of carbon and nutrient exchange are defined by the spatiotemporal heterogeneity of individual estuarine systems. Elemental stoichiometry provides a mechanism for simplifying overlapping physical, chemical, and biological drivers into proxies that can be used to compare and monitor estuarine biogeochemistry. To this end, the seasonal and tidal variability of estuarine stoichiometry was examined over an annual cycle in North Inlet (NI), South Carolina. Surface samples for dissolved and particulate carbon (C), nitrogen (N), and phosphorus (P) were collected every 20 days (August 2014 to August 2015) over a semi-diurnal tidal cycle. Dissolved nutrient flux estimates of an individual tidal creek were also made. Overall, the results demonstrated the dominance of seasonal versus tidal forcing on water column C:N:P stoichiometry. This seasonal behavior mediated the relative exchange of N and P into and out of the tidal creek and influenced the nutrient status index (NSI) of NI plankton communities. These communities were largely N deficient with the magnitude of this deficiency impacted by assumptions of inorganic versus organic plankton P demand and nutrient supply. Persistent N deficiency appeared to help drive the net import of N, while temporary P surplus likely drives its seasonal export. Combined, these results indicate that material delivery must be considered on seasonal time frames, as net annual fluxes do not reflect the short-term deliveries of C and nutrients into nearshore ecosystems.

State of the Art and Challenges for Offshore Integrated Multi-Trophic Aquaculture (IMTA)

By moving away from coastal waters and hence reducing pressure on nearshore ecosystems, offshore aquaculture can be seen as a possible step towards the large-scale expansion of the marine food production. Integrated multi-trophic aquaculture (IMTA) in nearshore water bodies has received increasing attention and could therefore play a role in the transfer of aquaculture operations to offshore areas. IMTA holds scope for multi-use of offshore areas and can bring environmental benefits from making use of waste products and transforming these into valuable co-products. Furthermore, they may act as alternative marine production systems and provide scope for alternative income options for coastal communities, e.g. by acting as nodes for farm operation and maintenance requirements. This paper summarizes the current state of knowledge on the implications of the exposed nature of the offshore and open ocean sites on the biological, technological and socio-economic performance of IMTA. Of particular interest is improving knowledge about resource flows between integrated species in hydrodynamic challenging conditions that characterise offshore waters.

Cell wall chemistry and tissue structure underlie shifts in material properties of a perennial kelp

ABSTRACTLaminaria is an abundant kelp genus in temperate nearshore ecosystems that grows with a circannual ‘stop-start’ pattern. Species of Laminaria play important ecological roles in kelp forests worldwide and are harvested commercially as a source of food and valuable extracts. In order to evaluate seasonal differences in tissue properties and composition, we compared the material properties, histology and cell-wall composition of overwintering blades with newly synthesized, actively growing blades from Laminaria setchellii. We found that overwintering blades were fortified with a thicker cortex and increased cell wall investment, leading to increased material strength. Overwintering tissues were composed of higher proportions of cellulose and fucose-containing polysaccharides (i.e. FCSPs, fucoidans) than newly formed blades and were found to possess thicker cell walls, likely to withstand the waves of winter storms. Chemical cell wall profiling revealed that significant proportions of fucose were associated with cellulose, especially in overwintering tissues, confirming the association between cellulose and some fucose-containing polysaccharides. Changes in material properties during the resting phase may allow these kelps to retain their non-growing blades through several months of winter storms. The results of this study demonstrate how one species might regulate its material properties seasonally, and at the same time shed light on the mechanisms that might control the material properties of kelps in general.

Eelgrass as Valuable Nearshore Foraging Habitat for Juvenile Pacific Salmon in the Early Marine Period

AbstractThe early marine period is a critical life history stage for growth and survival of anadromous juvenile Pacific salmon. The integrity of nearshore ecosystems where juvenile salmon reside and the capacity of these habitats to provide prey can thus influence overall salmon returns. Eelgrass Zostera marina beds in particular are considered critical nearshore habitat. By examining how juvenile salmon use this habitat during their early marine life, we gain insight into the trophic dynamics in these ecosystems and help gauge the effects of accelerating eelgrass loss and nearshore habitat development on juvenile salmon. This project investigated the role of eelgrass as juvenile salmon foraging habitat. We compared juvenile Chum Salmon Oncorhynchus keta and juvenile Chinook Salmon O. tshawytscha diets to prey availability in zooplankton tows and in epifaunal eelgrass samples across a gradient of eelgrass density in the Comox Estuary, British Columbia. Harpacticoid copepods dominated the diets of both juvenile Chum Salmon and Chinook Salmon and were found in abundance in eelgrass blades. We complemented diet analysis with carbon (δ13C) and nitrogen (δ15N) stable isotope analysis to examine the relative contribution of zooplankton, eelgrass epifaunal invertebrates, and terrestrial invertebrates to the diet of juvenile Chum Salmon. Juvenile Chum Salmon isotope ratios closely reflected those of eelgrass invertebrates, suggesting that eelgrass invertebrates made up approximately 80% of the diets of juvenile Chum Salmon. Our results highlight the value of eelgrass in providing nearshore foraging opportunities for juvenile salmon and suggest that eelgrass habitat protection and restoration may provide critical support for growth, thereby easing the transition of juvenile salmon from freshwater to the marine environment.

Water velocity modeling can delineate nearshore and main channel plankton environments in a large river

Methods to distinguish nearshore and main channel ecosystems within large rivers are essential for observing physical, chemical, and biological features that influence overall river ecosystem function. Water velocity fields based on hydrodynamic modeling of water flow trajectory were used to evaluate water history (i.e., water moving slowly as in a slack water region, or more rapidly, as characteristic of the main channel) prior to passing a given point in the Upper St. Lawrence River. Using this method to differentiate zones in the river, observations of biotic and abiotic variables in nearshore and main channel zones during late spring and summer (June–August) were compared to assess the difference in these water column river ecosystems. Differences in plankton community composition between nearshore and main channel waters along the Upper St. Lawrence River were investigated to test the hypothesis that nearshore and main channel environments in large river systems have different biotic (e.g., phytoplankton, crustacean zooplankton, and rotifer concentrations) and abiotic [e.g., water temperature, specific conductivity, silicate, colored dissolved organic matter (CDOM), and total phosphorus] characteristics. Nearshore water had significantly higher concentrations of CDOM and chlorophyll-a than main channel waters. With distance downstream, crustacean zooplankton and rotifers decreased in abundance in both nearshore and main channel regions. This study describes an effective method for stratified sampling design that differentiates nearshore and main channel ecosystems in the water column of large rivers.

Using underwater video to evaluate the performance of the Fukui trap as a mitigation tool for the invasive European green crab (Carcinus maenas) in Newfoundland, Canada.

The European green crab (Carcinus maenas) is a destructive marine invader that was first discovered in Newfoundland waters in 2007 and has since become established in nearshore ecosystems on the south and west coast of the island. Targeted fishing programs aimed at removing green crabs from invaded Newfoundland ecosystems use Fukui traps, but the capture efficiency of these traps has not been previously assessed. We assessed Fukui traps using in situ observation with underwater video cameras as they actively fished for green crabs. From these videos, we recorded the number of green crabs that approached the trap, the outcome of each entry attempt (success or failure), and the number of exits from the trap. Across eight videos, we observed 1,226 green crab entry attempts, with only a 16% rate of success from these attempts. Based on these observations we believe there is scope to improve the performance of the Fukui trap through modifications in order to achieve a higher catch per unit effort (CPUE), maximizing trap usage for mitigation. Ultimately, a more efficient Fukui trap will help to control green crab populations in order to preserve the function and integrity of ecosystems invaded by the green crab.

Formation, Fate, and Impacts of Microscopic and Macroscopic Oil‐Sediment Residues in Nearshore Marine Environments: A Critical Review

AbstractCrude oil that is spilled in marine environments often interacts with suspended sediments to form residues that can impact the recovery of the affected nearshore ecosystems. When spilled oil and sediment interact, they can form either small microscopic aggregates, commonly referred to as oil‐particle aggregates, or large macroscopic agglomerates, referred to as sediment‐oil agglomerates or sediment‐oil mats. Although these different sized oil‐sediment residues have similar compositions, they are formed under different conditions and have different fates in nearshore environments; the goal of this review is to synthesize our current understanding of these two types of residues. We believe that researchers who focus solely on studying either microscopic aggregates or macroscopic agglomerates could benefit from understanding the research findings available in the other field. In this study, we compare and contrast various processes that control the formation, fate, and impacts of these two types of residues in nearshore environments and point out some of the knowledge gaps in this field. Additionally, these residues have been referred to by many names in the past, leading to confusion and misconceptions at times. In this effort, we recommend a uniform nomenclature to distinguish them based on their physical size. Our overall aim is to bridge the gap between microscopic and macroscopic oil‐sediment residue literature to foster a robust exchange of ideas, which we believe can lead to the development of efficient strategies for managing oil spills that affect nearshore environments.

The Fate and Impact of Internal Waves in Nearshore Ecosystems.

Internal waves are widespread features of global oceans that play critical roles in mixing and thermohaline circulation. Similarly to surface waves, internal waves can travel long distances, ultimately breaking along continental margins. These breaking waves can transport deep ocean water and associated constituents (nutrients, larvae, and acidic low-oxygen waters) onto the shelf and locally enhance turbulence and mixing, with important effects on nearshore ecosystems. We are only beginning to understand the role internal waves play in shaping nearshore ecosystems. Here, I review the physics of internal waves in shallow waters and identify two commonalities among internal waves in the nearshore: exposure to deep offshore waters and enhanced turbulence and mixing. I relate these phenomena to important ecosystem processes ranging from extreme events to fertilization success to draw general conclusions about the influence of internal waves on ecosystems and the effects of internal waves in a changing climate.

Response of nearshore ecosystems to the Deepwater Horizon oil spill

Response of nearshore ecosystems to the Deepwater Horizon oil spill

Secondary Production of Macrobenthic Communities in Seagrass (Zostera marina, Eelgrass) Beds and Bare Soft Sediments Across Differing Environmental Conditions in Atlantic Canada

In nearshore ecosystems, habitats with emergent structure are often assumed to have higher ecosystem functioning than habitats lacking structure. However, such habitat-specific differences may depend on the surrounding environment. In this study, I examine the robustness of habitat-specific differences in ecosystem functioning for seagrass (Zostera marina) and adjacent bare soft sediments across varying environmental conditions on the Atlantic Coast of Nova Scotia, Canada, using secondary production as a metric. I also examine relationships of community secondary production and faunal structure with measured environmental variables (water depth, temperature, exposure, sediment, and plant properties). Benthic secondary production (invertebrates ≥500 μm) was higher in seagrass compared to bare sediments only at exposed sites with sandy sediments low in organic content, deep and cool water, and high belowground plant biomass. A regression relating community secondary production to the environmental variables explained 56% of the variance, while a constrained ordination explained 16% of the community structure. Important environmental determinants of community production were shoot density, temperature, depth, exposure, sediment organic content, and belowground plant biomass. Community structure was influenced by these variables plus sediment sand content and canopy height. This study shows that habitat-specific differences in secondary production may not be consistent across varying environmental conditions. Furthermore, seagrass beds are not always associated with higher ecosystem functioning than adjacent bare sediment. Both the surrounding environmental conditions and the presence of habitat structure should be considered for optimal management of nearshore ecosystems.

Coastal ocean acidification and increasing total alkalinity in the northwestern Mediterranean Sea

Abstract. Coastal time series of ocean carbonate chemistry are critical for understanding how global anthropogenic change manifests in near-shore ecosystems. Yet, they are few and have low temporal resolution. At the time series station Point B in the northwestern Mediterranean Sea, seawater was sampled weekly from 2007 through 2015, at 1 and 50 m, and analyzed for total dissolved inorganic carbon (CT) and total alkalinity (AT). Parameters of the carbonate system such as pH (pHT, total hydrogen ion scale) were calculated and a deconvolution analysis was performed to identify drivers of change. The rate of surface ocean acidification was −0.0028 ± 0.0003 units pHT yr−1. This rate is larger than previously identified open-ocean trends due to rapid warming that occurred over the study period (0.072 ± 0.022 °C yr−1). The total pHT change over the study period was of similar magnitude as the diel pHT variability at this site. The acidification trend can be attributed to atmospheric carbon dioxide (CO2) forcing (59 %, 2.08 ± 0.01 ppm CO2 yr−1) and warming (41 %). Similar trends were observed at 50 m but rates were generally slower. At 1 m depth, the increase in atmospheric CO2 accounted for approximately 40 % of the observed increase in CT (2.97 ± 0.20 µmol kg−1 yr−1). The remaining increase in CT may have been driven by the same unidentified process that caused an increase in AT (2.08 ± 0.19 µmol kg−1 yr−1). Based on the analysis of monthly trends, synchronous increases in CT and AT were fastest in the spring–summer transition. The driving process of the interannual increase in AT has a seasonal and shallow component, which may indicate riverine or groundwater influence. This study exemplifies the importance of understanding changes in coastal carbonate chemistry through the lens of biogeochemical cycling at the land–sea interface. This is the first coastal acidification time series providing multiyear data at high temporal resolution. The data confirm rapid warming in the Mediterranean Sea and demonstrate coastal acidification with a synchronous increase in total alkalinity.

Large-scale Dam Removals and Nearshore Ecological Restoration: Lessons Learned from the Elwha Dam Removals

Large dam removals are emerging as an important ecosystem restoration tool, and they often have direct influence on the marine nearshore zone, but dam removal plans give little consideration to nearshore restoration. We provide an overview of the relationship between large-scale dam removals and nearshore restoration, using the Elwha dam removal project, in Washington State, United States, as a basis. The following steps are essential for incorporating nearshore restoration planning into future dam removals: 1) Conceptual and technical modeling of nearshore physical and ecological processes at the drift cell scale to define nearshore priorities and geographic areas to be conserved or restored; 2) Acquiring seasonal field data to inform models, including: water quality; sediment delivery volumes, timing, trajectory and composition; and basic fish community data such as abundance, size, species composition, and trophic components; 3) Mapping nearshore habitat areal extent and ecological function prior to, during, and after dam removal, including vegetation composition and invertebrate community composition; 4) Defining and addressing the implications of habitat barriers and fish management actions for nearshore ecosystem function prior to dam removal. Structures and hatchery practices that conflict with nearshore ecosystem function for wild species prior to, during, and after dam removal should be identified and eliminated; 5) Anticipating nearshore invasive species colonization as a result of dam removal; 6) Developing and implementing long-term adaptive management plans to ensure nearshore restoration goals are identified and met. These steps must begin as early as possible in the planning process.