Isotopic ecology has been widely used to understand spatial connectivity and trophic interactions in marine systems. However, its potential for monitoring an ecosystem's health and function has been hampered by the lack of consistent sample storage and long-term studies. Preserved specimens from museum collections are a valuable source of tissue for analyses from ancient and pre-modern times, but isotopic signatures are known to be affected by commonly used fixatives. The aim of the present study was to understand the effects of fixatives on isotopic signatures of bulk tissue (d 13 C m and d 15 N m ) and amino acids (d 13 C AA and d 15 N AA ) of fish muscle and to provide correction equations for the isotopic shifts. Two specimens of each: blue cod (Parapercis colias), blue warehou (Seriolella brama), and king salmon (Oncorhynchus tschawytscha) were sampled at five locations along their dorsal musculature, at four time periods: (1) fresh, (2) after 1 month preserved in formalin, and after (3) 3 and (4) 12 months fixed in either ethanol or isopropanol. Lipid content was positively correlated with C: N ratio (r² = 0.83) and had a significant effect on d 13 C after treatments, but not on d 15 N. C:N ratio (for d 13 C m ) and percent N (for d 15 N m ) from preserved specimens contributed to the most parsimonious mixed models, which explained 79% of the variation due to fixation and preservation for d 13 C and 81% for d 15 N. d 13 C AA were generally not affected by fixatives and preservatives, while most d 15 N AA showed different signatures between treatments. d 15 N AA variations did not affect the magnitude of differences between amino acids, allowing scientists to retrieve ecological information (e.g., trophic level) independently of time under preservation. Corrections were applied to the raw data of the experiment, highlighting the importance of d 13 C m and d 15 N m correction when fish muscle tissues from wet collections are compared to fresh samples. Our results make it possible to retrieve d 13 C m , d 15 N m , d 13 C AA , and d 15 N AA from museum specimens and can be applied to some of the fundamental questions in ecology, such as trophic baseline shifts and changes in community's food web structure through time.Key words: amino acids; environmental change; food web; preserved fish; stable isotopes; trophic ecology. that the effect of a stressor on a given response variable will be greater than the inherent spatial heterogeneity of Manuscript

Variability in the abundance of commercial catches of fish has been studied for centuries (Huxley, 1881), especially in highly productive and highly populated regions (Heincke, 1898;Newland, 1999).Globally, abundance of fishing stocks has displayed declines over the past several decades (Worm et al., 2009), with changes in commercial fish assemblages identified for important fishing grounds

Regional differences in trophic structure and availability of alternate sources of basal organic matter to food webs can affect the volume of organic matter converted into fish biomass. The present study combined stable isotope analyses (δ 13 C and δ 15 N) with estimates of biomass density of 22 common reef fishes to compare supply of organic matter derived from macroalgae versus phytoplankton to reef fish communities among 30 sites distributed across Fiordland and the Marlborough Sounds, 2 contrasting regions in terms of land-based stressors on the South Island, New Zealand. Fish communities in the Marlborough Sounds were supported by food webs that incorporated less organic matter derived from macroalgae compared to those in Fiordland. Contribution of organic matter derived from macroalgae to fish biomass decreased with trophic level in the Marlborough Sounds, while fishes in Fiordland were supported by a more equal mixture of organic matter derived from phytoplankton and macroalgae among trophic levels. Total fish biomass density was 1.72 times higher in Fiordland, yet the fish community converted 2.91 times more organ ic matter to fish biomass, as a result of a higher proportion of biomass at high trophic levels. The observed patterns were consistent with limitation in supply of organic matter derived from macroalgae in the Marlborough Sounds, where extensive losses of kelp forest habitat linked to land-based stressors have been reported. The results highlight the importance of considering regional variability in basal organic matter source pools, particularly those produced from sensitive kelp forest habitats, when applying ecosystem-based approaches to managing coastal resources.

1. The relative availability of alternative organic matter sources directly influences trophic interactions within ecological communities. As differences in trophic ecology can alter the productivity of communities, understanding spatial variability in trophic structure, and the drivers of variability, is vital for implementing effective ecosystem-based management.2. Bulk stable isotope analysis (δ 13 C and δ 15 N) and mass balance calculations were used to examine patterns in the contribution of organic matter derived from macroalgae to food webs supporting temperate reef fish communities in two contrasting coastal waterways on the South Island of New Zealand: Fiordland and the Marlborough Sounds. Ten fish species common to both regions were compared, with up to 40% less organic matter from macroalgae supporting omnivorous species in the Marlborough Sounds. The largest differences in trophic position were found in those species exploited by fisheries.3. Furthermore, stratified surveys of abundance and species biomass combined with trophic position data were used to calculate regional differences in the contribution of macroalgae to whole fish communities in terms of density of biomass. In Fiordland, over 77% of the biomass of exploited reef fishes was supported by macroalgae, compared with 31% in the Marlborough Sounds. 4. Surveys of macroalgal density and species composition in the two regions indicated that regional differences in trophodynamics may be explained by a lack of macroalgal inputs to the food web in the Marlborough Sounds.5. The findings demonstrate large regional differences in the incorporation of benthic and pelagic sources of organic matter to food webs supporting reef fish communities, highlighting the need for ecosystem-based approaches to management to recognize spatial variability in primary production supporting coastal food webs.

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In 1979, the Suess effect was described as decreasing δ13C in the oceans linked to anthropogenic CO2 emissions. After years of over-fertilization of farming soils and runoff, we hypothesized that δ15N in coastal environments would also decline, whereby synthetic fertilizers lead to depletion of the heavy isotope 15N. We used museum-preserved and modern samples of 3 fishes from Otago, New Zealand, to reconstruct the isotopic baselines of C and N and assess specific trophic positions through time (1955-present) based on bulk and amino acid stable isotope values. Our sample set included Odax pullus, a strictly herbivorous species, and 2 commercially important species: Nemadactylus macropterus and Parapercis colias. Muscle tissue of the fishes recorded the change in δ13CBulk through time, which matched estimated Suess effect values for New Zealand. We also resolved the effects on the C isotopic baseline from natural changes in the food web using analysis of the δ13C of essential amino acids and found that while P. colias maintained a steady diet, the food web position of N. macropterus likely changed. Analysis of δ15N of phenylalanine in O. pullus indicated a decrease of 0.023‰ yr-1 since 1955, which corroborates our coastal N-enrichment hypothesis. Furthermore, we found that isotopic changes for N. macropterus were consistent with overfishing and habitat degradation in the region. These data provide vital information for our resolution and understanding of how past environments have changed in terms of both anthropogenic influences on coastal food web structure and biogeochemical cycles of C and N in marine ecosystems.

Palythoa caribaeorum is a zoanthid often dominant in shallow rocky environments along the west coast of the Atlantic Ocean, from the tropics to the subtropics. This species has high environmental tolerance and is a good space competitor in reef environments. Considering current and future scenarios in the global climate regime, this study aimed to model and analyze the distribution of P. caribaeorum, generating maps of potential distribution for the present and the year 2100. The distribution was modeled using maximum entropy (Maxent) based on 327 occurrence sites retrieved from the literature. Calcite concentration, maximum chlorophyll-a concentration, salinity, pH, and temperature range yielded a model with the smallest Akaike information criterion (2649.8), and were used in the present and future distribution model. Data from the HadGEM2-ES climate model were used to generate the projections for the year 2100. The present distribution of P. caribaeorum shows that parts of the Brazilian coast, Caribbean Sea, and Florida are suitable regions for the species, as they are characterized by high salinity and pH and small temperature variation. An expansion of the species’ distribution was forecast northward under mild climate scenarios, while a decrease of suitable areas was forecast in the south. In the climate scenario with the most intense changes, P. caribaeorum would lose one-half of its suitable habitats, including the northernmost and southernmost areas of its distribution. The Caribbean Sea and northeastern Brazil, as well as other places under the influence of coastal upwellings, may serve as potential havens for this species.

Aim Fisheries ecosystems are subject to long‐term shifts in food web structure as a result of exploitation and environmental change. These shifts can be gradual and unresolved by decadal‐scale time series. The aim of our study was to determine long‐term legacy effects of overexploitation and changes to the composition of basal organic matter sources on the trophic structure of marine food webs. Location New Zealand. Time period Approximately 1250 AD to the present; the complete history of human occupation in New Zealand. Major taxa studied Mesopredatory fishes. Methods We used whole tissue (δ13C and δ15N) and amino acid‐specific (δ15NAA) stable isotope analyses of bone collagen and muscle tissue from five fishes spanning the period of human occupation of New Zealand to resolve the bioenergetic consequences of long‐term shifts in food web structure. Stable isotope analysis of amino acids provided the basis for resolution of changes in trophic level in the absence of information on δ15N at the base of the food web during pre‐industrial times. Results Our analyses indicate likely declines in the contribution of organic matter derived from kelps in four species, and intraspecific increases in trophic levels in three species of the five fishes studied between European colonization (AD 1650–1800) and the present‐day regime of industrialized fishing and environmental change (AD 1953–2018), but little change during the prehistoric time period spanning early Māori occupation (AD 1250–1450) to European colonization. Analysis of the bioenergetic costs of the observed shifts in food web structure indicate a 179% increase in basal organic matter requirements to support mesopredatory fish. Main conclusions These data provide a rare case study on the consequences of legacy effects of exploitation and environmental change for bioenergetics of fish communities relevant to ongoing changes in global marine ecosystems. Overexploitation and decline in kelp forests have inflated the bioenergetic costs of these fisheries.