Eelgrass Habitat Research Articles

Microbial Detoxification of Sediments Underpins Persistence of Zostera marina Meadows.

Eelgrass meadows have attracted much attention not only for their ability to maintain marine ecosystems as feeding grounds for marine organisms but also for their potential to store atmospheric and dissolved CO2 as blue carbon. This study comprehensively evaluated the bacterial and chemical data obtained from eelgrass sediments of different scales along the Japanese coast to investigate the effect on the acclimatization of eelgrass. Regardless of the eelgrass habitat, approximately 1% Anaerolineales, Babeliales, Cytophagales, and Phycisphaerales was present in the bottom sediment. Sulfate-reducing bacteria (SRB) were present at 3.69% in eelgrass sediment compared to 1.70% in bare sediment. Sulfur-oxidizing bacteria (SOB) were present at 2.81% and 1.10% in the eelgrass and bare sediment, respectively. Bacterial composition analysis and linear discriminant analysis revealed that SOB detoxified H2S in the eelgrass meadows and that the larger-scale eelgrass meadows had a higher diversity of SOB. Our result indicated that there were regional differences in the system that detoxifies H2S in eelgrass meadows, either microbial oxidation mediated by SOB or O2 permeation via the physical diffusion of benthos. However, since bacterial flora and phylogenetic analyses cannot show bias and/or causality due to PCR, future kinetic studies on microbial metabolism are expected.

원격탐사자료와 GIS를 활용한 연안해역 잘피 분포 특성

원격탐사자료와 GIS를 활용한 연안해역 잘피 분포 특성

Stable isotopes reveal intertidal fish and crabs use bivalve farms as foraging habitat in Puget Sound, Washington

Bivalves such as oysters and clams have been farmed in intertidal zones across the Puget Sound region of the Salish Sea for thousands of years. The variety of gear types used on bivalve farms creates complex vertical structure and attachment points for aquatic epiphytes and invertebrates which increases habitat structural complexity, but may alter eelgrass cover in areas where bivalve farms and eelgrass meadows overlap. Eelgrass meadows are highly productive and ecologically foundational nearshore habitats that provide valuable ecosystem services including the provision of nursery, refuge, and foraging habitat. Aquaculture has been a key feature of the environment in the Puget Sound for millennia, however, little is known about how well aquaculture practices are integrated into the system, and what services they provide to mobile species assemblages relative to unfarmed eelgrass meadows. We used stable isotope mixing models to estimate, for several species of nearshore fish and crab in two areas of North Puget Sound, Washington, the percent diet originating from either a natural bottom habitat (eelgrass meadows), farm habitat (oyster farms), or pelagic planktonic sources. Our results indicate that several species of nearshore fish such as surf perch and staghorn sculpin derive a significant proportion of their diets from farm areas, while crabs derive most of their diets from eelgrass habitat, and stickleback derive a significant proportion of their diets from planktonic sources. The results indicate that foraging habitat uses are species specific, and that several species that spatially overlap bivalve farms obtained a large percentage of their diets from adjacent bivalve farm habitat.

Eelgrass habitat structure affects epifaunal biodiversity and community composition but not the distribution of functional traits among taxa

Eelgrass habitat structure affects epifaunal biodiversity and community composition but not the distribution of functional traits among taxa

Lessons learned from over thirty years of eelgrass restoration on the US West Coast

AbstractSeagrass habitats, which provide essential ecosystem functions such as water quality improvement, biodiversity support, ocean acidification amelioration, and sediment carbon storage, are declining worldwide. Eelgrass (Zostera marina) habitats along the contiguous US West Coast are threatened by conflicting human uses and global change, resulting in significant protections of and efforts to restore areas where habitat is extant or degraded. Despite a history of eelgrass restoration in this region spanning nearly 60 years, very little work has been published on the subject. Here, we review all available literature on eelgrass restoration projects conducted in California, Oregon, and Washington. Of the 82 restoration projects included in this analysis, which were conducted from 1989 to 2020, only 6 were published in peer‐reviewed journals. Thus, despite the precedent for conducting restoration, a lack of data availability makes assessing regional success, drivers of failure, and best practices extremely difficult. From this synthesis, we find that the majority of restoration projects (73%) have been conducted for mitigation (compliance) purposes, contributing to the lack of peer‐reviewed literature on the subject. We find that while eelgrass mitigation policies serve to maintain eelgrass structure and regional acreages, they do not facilitate assessments of habitat function or incentivize advancements in regional best practices. We also find that when we could evaluate project outcomes, 32.3%–59.6% of restoration plots were unsuccessful by the end of the project, but this percentage is highly dependent on how success is defined. According to restoration practitioners, failure was likely to result from environmental factors such as light, nutrients, or macroalgal blooms, but was occasionally due to logistical factors such as restoration method or approach. From this work, we recommend a standardized, evidence‐based approach to restoration, improved data sharing practices, and careful consideration of existing eelgrass mitigation practices. As marine habitat restoration enters a new global stage, backed by public and private investment, burgeoning carbon markets, and global biodiversity initiatives, it is essential to learn from past work to understand and improve seagrass conservation and restoration success.

Eelgrass Meadow Edge Habitat Heterogeneity Enhances Fish Diversity on the Pacific Coast of Canada

Eelgrass (Zostera marina) meadows are important fish habitats in temperate coastal areas. Understanding the relationships between seascape patterns—the spatial and temporal variability of biological and physiochemical drivers—and fish diversity in eelgrass meadows is crucial to conserving and managing these important habitats. The main objective of this study was to determine the environmental variables that influence the diversity of fish in eelgrass meadows in British Columbia, and whether a rich mosaic of edge habitats is positively associated with species richness and diversity, owing to the increased niche dimensionality and foraging opportunities provided by heterogeneous adjacent habitats. Using a spatiotemporal multispecies model based on long-term eelgrass fish diversity monitoring program data (2004–2020), we found that seascape variables, particularly those derived from unmanned aerial vehicles (meadow area, edge habitat heterogeneity), explained the most variation in species occurrence and abundance. We also found a positive effect of edge habitat heterogeneity on species richness in small and medium-sized meadows, with higher species richness and diversity in small and medium-sized meadows with high edge habitat heterogeneity. The relationship between edge habitat heterogeneity and species richness and diversity in large meadows was less clear. We also found that species richness has declined through time while diversity has been variable through time, remaining relatively stable in one region and generally decreasing in the other region. This analysis provides key insights into how seascape variables influence the distribution of species and the diversity of fish assemblages in nearshore eelgrass habitats in British Columbia.

Flushing time variability in a short, low-inflow estuary

Flushing time, the time scale for exchange and mixing between embayed and oceanic waters in an estuary, plays an integral role in determining water quality and aquatic ecosystem health. Here, we investigated the spatiotemporal variability of flushing times throughout Morro Bay, a short, low-inflow estuary (LIE) on the California coast, using a calibrated and validated hydrodynamic model (Delft3D). Morro Bay has historically supported an extensive eelgrass (Zostera marina) habitat, which declined substantially from 139 to 5.4 ha during 2007–2017. Eelgrass decline motivated the current research into the role of changing bed roughness and oceanic drivers (i.e., tide and sea-level rise) on estuarine hydrodynamics and flushing times. We found that tidal variability exerts the strongest control on flushing times compared to other effects, i.e., bed roughness or sea-level rise. Additionally, we found that increasing sea level and decreasing bed roughness (associated with declining seagrass coverage) yielded higher rates of mixing (lower flushing times). We detected a strong correspondence between areas having shorter flushing times (e.g., near the estuary mouth) and areas occupied by resilient eelgrass populations in Morro Bay. Our findings further indicated that flushing times in short LIEs are particularly sensitive to several factors (e.g., bed roughness, sea level) that are susceptible to anthropogenic disturbance and future climate change.

A blessing or a curse: Responses of eelgrass (Zostera marina) seedlings to combined stressors of nutrients, hypoxia and sulfide

Eelgass (Zostera marina) beds have many functions; however, eelgrass populations have declined in recent decades. Thus, it is important to recover eelgrass populations. Multiple stressors coexist in eelgrass habitats and it is considered that stressors reduce the eelgrass population. Nevertheless, many seedlings are established under combined stressors. It is speculated that there are antagonistic and synergistic effects among these stressors, and the interaction between them determines the seedling fate. To verify this hypothesis, 840 eelgrass seedlings were exposed to combined stressors of nutrients, hypoxia and sulfide for 7 d. All of the seedlings survived. The pH of the experimental system decreased from the 0th to 24th h, but it increased after the 72nd h. The root activity was 119.87±5.48 μg.g−1.h−1 and was inhibited by the interaction of dissolved oxygen (DO) and ammonia, and increased with nitrate and the interaction of phosphate and sulfide. Both the proline content and the Chl a content were not affected by the stressors. The Chl b content was 0.14±0.16 mg.g−1 (calculated by wet weight) and was reduced by nitrate. The ratio of Chl a content to Chl b content was 2.53±0.07 and was affected by the stressors. There is antagonism and synergy among these stressors and the interaction of them determines seedling survival. Nitrate at a high concentration leads to seedling death. It is not accidental that seedlings survive or die under combined stressors, and the intensity and the spatiotemporal distribution of environmental stressors determine the recruitment of seedlings. Targeted habitat improvement contributes to the survival of eelgrass seedlings.

Influence of seagrass on juvenile Pacific oyster growth in two US west coast estuaries with different environmental gradients

Ocean acidification threatens many marine organisms, including oysters. Seagrass habitat has been suggested as a potential refuge for oysters because it may ameliorate stressful carbonate chemistry and augment food availability. We conducted an in situ study to investigate whether eelgrass Zostera marina habitat affects the growth of juvenile Pacific oysters Crassostrea gigas and influences local carbonate chemistry or food quantity at sites where we expected contrasting conditions in two US west coast estuaries. Juvenile oysters were out-planted in typical intertidal on-bottom (just above sediment) and off-bottom (45 cm above sediment) culture positions and in adjacent eelgrass and unvegetated habitats from June to September 2019. Water quality was measured with sondes for 24 h periods each month, and discrete water samples were collected in conjuncture. Results show that eelgrass habitat did not alter average local carbonate chemistry (pH, pCO2, Ωcalcite), but consistently reduced available food (relative chlorophyll a). Eelgrass habitat had little to no effect on the shell or tissue growth of juvenile oysters but may have influenced their energy allocation; oysters displayed a 16% higher ratio of shell to tissue growth in eelgrass compared to unvegetated habitat when cultured on-bottom. At the seascape scale, average site-level pH was negatively correlated with shell to tissue growth but not with shell growth alone. Overall, these findings suggest that juvenile oysters may display a compensatory response and allocate more energy to shell than tissue growth under stressful conditions like acidic water and/or altered food supply due to reduced immersion or eelgrass presence.

Ensemble habitat suitability modeling for predicting optimal sites for eelgrass (Zostera marina) in the tidal lagoon ecosystem: Implications for restoration and conservation

Seagrass systems are in decline, mainly due to anthropogenic pressures and ongoing climate change. Implementing seagrass protection and restoration measures requires accurate assessment of suitable habitats. Commonly, such assessments have been performed using single-algorithm habitat suitability models, nearly always based on low environmental resolution information and short-term species data series. Here we address eelgrass (Zoostera marina) meadows’ large-scale decline (>80%) in Shandong province (Yellow Sea, China) by developing an ensemble habitat model (EHM) to inform eelgrass conservation and restoration strategies in the Swan Lake (SL). For this, we applied a weighted EHM derived from ten single-algorithm models including profile, regression, classification, and machine learning methods to generate a high-resolution habitat suitability map. The EHM was constructed based on the predictive performances of each model, by combining a series of present-absent eelgrass datasets from recent years coupled with oceanographic and sediment data. The model was cross-validated with independent historical datasets, and a final habitat suitability map for conservation and restoration was generated. Our EHM scheme outperformed all single models in terms of habitat suitability, scoring ∼0.95 for both true statistic skill (TSS) and area under the curve (AUC) performance criteria. Machine learning methods outperformed profile, regression and classification methods. Regarding model explanatory variables, overall, topographic characteristics such as depth (DEP) and seafloor slope (SSL) are the most significant factors determining the distribution of eelgrass. The EHM predicted that the overlapping area was almost 90% of the current eelgrass habitat. Using results from our EHM, a LOESS regression model for the relationship of the habitat suitability to both the biomass and density of Z. marina outperformed better than the classic Ordinary Least Squares regression model. The EHM is a promising tool for supporting eelgrass protection and restoration areas in temperate lagoons as data availability improves.

Grazing preference and isotopic contributions of kelp to Zostera marina mesograzers

In seagrass food webs, small invertebrate mesograzers often exert top-down control on algal epiphytes growing on seagrass blades, which in turn releases the seagrass from competition for light and nutrients. Yet, nearshore habitat boundaries are permeable, and allochthonous subsidies can provide alternative food sources to in-situ production in seagrass meadows, which may in turn alter mesograzer-epiphyte interactions. We examined the contribution of allochthonous kelp (Nereocystis luetkeana), autochthonous epiphytic macroalgal (Smithora naiadum), Ulva lactuca, and seagrass production to mesograzer diets in a subtidal Zostera marina (eelgrass) meadow. In both choice feeding experiments and isotopic analysis, mesograzer diets revealed a preference for allochthonous N. luetkeana over Z. marina, S. naiadum, and U. lactuca. Notably, Idotea resecata showed an ~20x greater consumption rate for N. luetkeana in feeding experiments over other macrophytes. In the meadow, we found a positive relationship between epiphytic S. naiadum and gammarid amphipod biomass suggesting weak top-down control on the S. naiadum biomass. Epiphyte biomass may be driven by bottom-up factors such as environmental conditions, or the availability and preference of allochthonous kelp, though further work is needed to disentangle these interactions. Additionally, we found that gammarid and caprellid amphipod biomass were positively influenced by adjacency to kelp at seagrass meadow edges. Our findings suggest that N. luetkeana kelp subsidies are important to the diets of mesograzers in Z. marina meadows. Spatial planning and management of marine areas should consider trophic linkages between kelp and eelgrass habitats as a critical seascape feature if the goal is to conserve nearshore food web structure and function.

Under‐Ice Hydrography of the La Grande River Plume in Relation to a Ten‐Fold Increase in Wintertime Discharge

AbstractA large under‐ice plume forms because of the regulated winter discharge from the La Grande River hydroelectric complex (NE James Bay, Canada), which is among the largest winter discharges in the circumpolar north. In 2016–2017, field campaigns were completed to characterize the under‐ice plume's structure, extent, and short‐term dynamics related to tides, weather, and discharge. Amid concerns of the freshwater's impact on eelgrass, the lateral spreading of the under‐ice plume into inshore areas was also assessed. When discharges averaged 4,800 m3 s−1 throughout the January–March periods, the freshwater influence of La Grande River extended more than 100 km north along the James Bay coast, with the brackish (salinity <25) under‐ice plume more than three times larger than for a natural winter discharge of ∼460 m3 s−1. The core area of the under‐ice plume, defined as the area with a highly stratified water column and surface layer of salinity <5, extended 30–35 km north and >20 km south. It was stable throughout the January–March 2016–2017 periods and, despite 30% higher winter discharge, was not significantly larger compared to survey periods in 1984–1987. This stability appears to be due to coastal geometry and width of the landfast ice cover, under which the plume can spread with limited mixing. Inshore salinity was about 5–10 units lower in winter versus the open‐water period. The seasonal duration of reduced salinity at eelgrass habitats will depend on landfast ice duration as well as river discharge magnitude.

Fine-scale ensemble species distribution modeling of eelgrass (Zostera marina) to inform nearshore conservation planning and habitat management

Baseline data on the distribution and extent of biogenic habitat-forming species at a high spatial resolution are essential to inform habitat management strategies, preserve ecosystem integrity, and achieve effective conservation objectives in the nearshore. Model-based approaches to map suitable habitat for these species are a key tool to address this need, filling in gaps where observations are otherwise unavailable and remote sensing methods are limited by turbid waters or cannot be applied at scale. We developed a high resolution (35 m) ensemble species distribution model to predict the distribution of eelgrass (Zostera marina) along the Atlantic coast of Nova Scotia, Canada where the observational coverage of eelgrass occurrence is sparse and nearshore waters are optically complex. Our ensemble model was derived as a performance-weighted average prediction of 7 different modeling methods fit to 6 physical predictors (substrate type, depth, wave exposure, slope, and two bathymetric position indices) and evaluated with a 5-fold spatially-blocked cross-validation procedure. The ensemble model showed moderate predictive performance (Area Under the Receiver-Operating Characteristic Curve (AUC) = 0.803 ± 0.061, True Skill Statistic (TSS) = 0.531 ± 0.100; mean ± SD), high sensitivity (92.0 ± 4.5), and offered some improvement over individual models. Substrate type, depth, and relative wave exposure were the most influential predictors associated with eelgrass occurrence, where the highest probabilities were associated with sandy and sandy-mud sediments, depths ranging 0 m – 4 m, and low to intermediate wave exposure. Within our study region, we predicted a total extent of suitable eelgrass habitat of 38,130 ha. We found suitable habitat was particularly extensive within the long narrow inlets and extensive shallow flats of the South Shore, Eastern Shore, and Bras d’Or Lakes. We also identified substantial overlap of eelgrass habitat with previously identified Ecologically and Biologically Significant Areas that guide regional conservation planning while also highlighting areas of greater prediction uncertainty arising from disagreement among modeling methods. By offering improved sensitivity and insights into the fine-scale regional distribution of a habitat-forming species with associated uncertainties, our ensemble-based modeling approach provides improved support to numerous nearshore applications including conservation planning and restoration, marine spatial and emergency response planning, environmental impact assessments, and fish habitat protection.

Warming northward shifting southern limits of the iconic temperate seagrass (Zostera marina)

SummaryGlobal warming can shift the range edges of numerous species poleward. Here, eelgrass distribution was reinvestigated at its southern limits on the eastern coast of China, which indicated that there has been a northward shift in the southern limit of Z. marina. To determine if regional warming resulted in a northward shift in suitable eelgrass habitats, sixteen transplantations of adult eelgrass shoots and seeds at the historical southern distribution limit of eelgrass were conducted between 2016 and 2021. The results showed that high water temperatures in summer had negative effects on eelgrass growth, and directly triggered shoot mortality during 2016–2018. Under heat stress, antioxidant enzyme activity was initially increased, but then decreased under more stressful heat conditions; and the HSP70 protein and its molecular chaperone protein were highly expressed under heat stress. These results demonstrated that suitable eelgrass habitat was now located further north along the eastern coast of China.

Leveraging eDNA metabarcoding to characterize nearshore fish communities in Southeast Alaska: Do habitat and tide matter?

AbstractNearshore marine habitats are critical for a variety of commercially important fish species, but assessing fish communities in these habitats is costly and time‐intensive. Here, we leverage eDNA metabarcoding to characterize nearshore fish communities near Juneau, Alaska, USA, a high‐latitude environment with large tidal swings, strong currents, and significant freshwater input. We investigated whether species richness and community composition differed across three habitat types (sand beaches, eelgrass beds, and rocky shorelines) and between high and low tides. Additionally, we tested whether replication of field samples and PCR reactions influenced either species richness or composition. We amplified a 12S mitochondrial locus in our samples and identified 167 fish amplicon sequence variants, which were grouped into 24 unique taxa based on sequence similarity, with approximately half of these taxa resolved to single species. Species richness and composition inferred from eDNA differed substantially among habitats, with rock habitats containing fewer taxa and fewer overall detections than sand and eelgrass habitats. The effect of tide was not significant on its own, but a significant habitat‐tide interaction was documented, with the most pronounced differences in taxa between tides found in sand habitats. Power analyses indicated that additional field sampling is useful to detect small changes in species richness such as those due to tide. PCR replicates typically identified few additional taxa. Our results provide important information that can be used to guide future studies, most notably, that the influence of tide on eDNA results appears to be minimal and potentially isolated to certain habitats. This suggests that replication across tides may not be vital for future eDNA studies and that additional replication across space—particularly across heterogeneous environments—likely is a better allocation of sampling effort.

Sand-capping stabilizes muddy sediment and improves benthic light conditions in eutrophic estuaries: Laboratory verification and the potential for recovery of eelgrass (Zostera marina)

Decades of eutrophication have increased water turbidity in Danish estuaries and led to light limitation of eelgrass (Zostera marina) growth. Former eelgrass areas are now denuded and consist of organic-rich muddy sediment with frequent resuspension events that maintain a high turbidity state. In addition, low anchoring capacity of eelgrass in the soft organic-rich sediments has contributed to eelgrass loss. When navigation channels in Danish estuaries are dredged, large amounts (~100.000 m3) of sandy sediment are shipped to remote dumping sites. Instead, we suggest that the dredged sand is used to consolidate adjacent muddy areas. We demonstrate in the present laboratory study that capping of fluid muddy sediment with 10 cm of sand is feasible without any vertical mixing and that this marine restoration approach potentially can lower the magnitude and frequency of resuspension events. Erosion of suspended solids change from 5 g m−2 min−1 above muddy sediment as to about 0.2 g m−2 min−1 after sand-capping, implying that the application of sand can improve light conditions. Moreover, since erosion thresholds increase from about 10–12 cm s−1 for mud to 40 cm s−1 for sand-capped mud the anchoring capacity of rooted vegetation is increased. However, the full potential of sand-capping to facilitate restoration of otherwise lost eelgrass habitats requires verification by large-scale field experiments.

The Green Wave: reviewing the environmental impacts of the invasive European green crab (Carcinus maenas) and potential management approaches

The European green crab (Carcinus maenas), native to northwestern Europe and Africa, is among the top 100 most damaging invasive species globally. In some regions, including the Atlantic coast of North America, C. maenas has caused long-term degradation of eelgrass habitats and bivalve, crab, and finfish populations, while other areas are near the beginning of the invasion cycle. Owing to the high persistence and reproductive potential of C. maenas populations, most local and regional mitigation efforts no longer strive for extirpation and instead focus on population control. Long-term monitoring and rapid response protocols can facilitate early detection of introductions that is critical to inform management decisions related to green crab control or extirpation. Once C. maenas are detected, local area managers will need to decide on management actions, including whether and what green crab control measures will be implemented, if local invasion might be prevented or extirpated, and if population reduction to achieve functional eradication is achievable. Owing to the immense operational demands likely required to extirpate C. maenas populations, combined with the limited resources for monitoring and removal, it is unlikely that any single government, conservation, and (or) academic organization would be positioned to adequately control or extirpate populations in local areas, highlighting the importance of collaborative efforts. Community-based monitoring, and emerging methods such as environmental DNA (eDNA) may help to expand the spatial and temporal extent of monitoring, facilitating early detection and removal of C. maenas. While several C. maenas removal programs have succeeded in reducing their populations, to our knowledge, no program has yet successfully extirpated the invader, and the cost of any such program would likely be immense and unsustainable over the long-term. An alternative approach is functional eradication, whereby C. maenas populations are reduced below threshold levels such that ecosystem impacts are minimized. Less funding and effort would likely be required to achieve and maintain compared to extirpation. In either case, continual control efforts will be required because C. maenas populations can quickly increase from low densities and larval re-introductions.

Characterizing the habitat function of bivalve aquaculture using underwater video

Bivalve aquaculture is an expanding coastal industry with the potential to modify the habitat of fish and crab species, affecting their refuge, movement, and feeding. The habitat function of shellfish aquaculture is not yet well understood, in part due to difficulties in data collection using traditional methods. Underwater video was used to observe fish and crab species’ affiliations with cultured Pacific oyster Crassostrea gigas and Manila clam Venerupis philippinarum aquaculture sites in comparison to uncultured reference sediment and eelgrass habitats. Sites were monitored in 9 locations across 3 regions of Puget Sound, Washington, USA, in the summers of 2017 and 2018. Of the 3038 fish and crabs observed, 98% were represented by Embiotocidae (surfperch), crabs, three-spined stickleback Gasterosteus aculeatus, Cottidae (sculpins), and Pleuronectiformes (flatfish). Overall, the affiliations of fish and crabs with bivalve aquaculture varied by species groups, culture type, and regional environmental and habitat conditions. These interactions varied on a scale of approximately 150 km, highlighting variation of aquaculture-ecological interactions at a scale not previously recorded in Puget Sound. Species composition varied between aquaculture and non-aquaculture habitats in 2 of the 3 regions studied. Species diversity and richness in aquaculture habitats varied regionally, relative to reference habitats. Pelagic species were more abundant in aquaculture and reference sites that had vertical structure, but abundances of demersal and benthic species on aquaculture habitat relative to reference sites varied regionally. The availability of habitats within intertidal regions, including varying types of aquaculture, could determine community structure for marine organisms such as fish and crab.

Environmental compensation for biodiversity and ecosystem services: A flexible framework that addresses human wellbeing

Environmental compensation should address negative impacts from human activities on nature, including loss of biodiversity and ecosystem services. However, successful compensation, achieving no net loss, requires broad quantitative information on different types of losses and gains. We find that the scope of compensatory schemes varies in what is considered compensable, which makes it challenging to apply a conceptual approach consistently across schemes with different needs. We propose a flexible yet structured framework for determining which values should be compensated and how. Our framework focuses specifically on habitat deterioration and is illustrated with a case study involving loss of eelgrass habitat. The framework helps identify compensation needs and selects among suitable compensation options, merging science-based information with normative issues and local concerns. By integrating the ecosystem services cascade model, it encompasses aspects from biodiversity structure to human wellbeing. The framework prefers in-kind compensation because this targets the structure level and thus meets compensation needs in all subsequent levels of the cascade model; further, it is more likely to capture non-instrumental values (i.e. in nature) and reduce exposure to uncertainty. We highlight the importance of spatial aspects of ecosystem functions, services and their subsequent impacts on wellbeing. Although our selection hierarchy assumes a “similar and nearby” principle for habitat restoration (preference for in-kind/on-site), this criterion is not universal. We underscore the hierarchy’s implicit normative assumptions and suggest that apparent disagreement about who should benefit may be traced to an unresolved conflict between egalitarianism and utilitarianism.

Seagrass and Oyster Reef Restoration in Living Shorelines: Effects of Habitat Configuration on Invertebrate Community Assembly

Restoration projects provide a valuable opportunity to experimentally establish foundational habitats in different combinations to test relative effects on community assembly. We evaluated the development of macroinvertebrate communities in response to planting of eelgrass (Zostera marina) and construction of reefs intended to support the Olympia oyster (Ostrea lurida) in the San Francisco Estuary. Plots of each type, alone or interspersed, were established in 2012 in a pilot living shorelines project, and quarterly invertebrate monitoring was conducted for one year prior to restoration, and three years post-restoration using suction sampling and eelgrass shoot collection. Suction sampling revealed that within one year, oyster reefs supported unique invertebrate assemblages as compared to pre-restoration conditions and controls (unmanipulated mudflat). The eelgrass invertebrate assemblage also shifted, becoming intermediate between reefs and controls. Interspersing both types of habitat structure led eelgrass invertebrate communities to more closely resemble those of oyster reefs alone, though the eelgrass assemblage maintained some distinction (primarily by supporting gammarid and caprellid amphipods). Eelgrass shoot collection documented some additional taxa known to benefit eelgrass growth through consumption of epiphytic algae; however, even after three years, restored eelgrass did not establish an assemblage equivalent to natural beds, as the eelgrass sea hare (Phyllaplysia taylori) and eelgrass isopod (Pentidotea resecata) remained absent or very rare. We conclude that the restoration of two structurally complex habitat types within tens of meters maximized the variety of invertebrate assemblages supported, but that close interspersion dampened the separately contributed distinctiveness. In addition, management intervention may be needed to overcome the recruitment limitation of species with important roles in maintaining eelgrass habitat.