Aquatic biodiversity enhances multiple nutritional benefits to humans

Abstract

Humanity depends on biodiversity for health, well-being, and a stable environment. As biodiversity change accelerates, we are still discovering the full range of consequences for human health and well-being. Here, we test the hypothesis-derived from biodiversity-ecosystem functioning theory-that species richness and ecological functional diversity allow seafood diets to fulfill multiple nutritional requirements, a condition necessary for human health. We analyzed a newly synthesized dataset of 7,245 observations of nutrient and contaminant concentrations in 801 aquatic animal taxa and found that species with different ecological traits have distinct and complementary micronutrient profiles but little difference in protein content. The same complementarity mechanisms that generate positive biodiversity effects on ecosystem functioning in terrestrial ecosystems also operate in seafood assemblages, allowing more diverse diets to yield increased nutritional benefits independent of total biomass consumed. Notably, nutritional metrics that capture multiple micronutrients and fatty acids essential for human well-being depend more strongly on biodiversity than common ecological measures of function such as productivity, typically reported for grasslands and forests. Furthermore, we found that increasing species richness did not increase the amount of protein in seafood diets and also increased concentrations of toxic metal contaminants in the diet. Seafood-derived micronutrients and fatty acids are important for human health and are a pillar of global food and nutrition security. By drawing upon biodiversity-ecosystem functioning theory, we demonstrate that ecological concepts of biodiversity can deepen our understanding of nature's benefits to people and unite sustainability goals for biodiversity and human well-being.

Keywords: biodiversity–ecosystem functioning; ecosystem services; seafood.

Fig. 1.

Aquatic biodiversity increases human well-being because edible species have distinct and complementary multinutrient profiles (A) and differ in mean micro- and macronutrient content (shown here relative to 10 and 25% thresholds of recommended dietary allowance, RDA, guidelines) for representative finfish (Abramis brama, Mullus surmuletus), mollusc (Mytilus galloprovincialis), and crustacean species (Nephrops norvegicus). Biodiversity–ecosystem functioning theory predicts that nutritional benefits, including the number of nutrient RDA targets met per 100 g portion (NT; i, iii) and minimum portion size (P_min; ii, iv) (B and E), are enhanced with increasing seafood species richness. Orange dots in B and E correspond to potential diets of high and low biodiversity levels. Seafood consumers with limited access to seafood each day may not reach RDA targets if diets are low in diversity (D–F versus A–C; gray shading indicates proportion of population that meets nutrient requirements). DHA: docosahexaenoic acid, EPA: eicosapentaenoic acid.

Fig. 2.

Variation in nutrient concentrations differs among taxonomic groups. (Upper) Frequency of reported protein, fat, micronutrient and fatty acid content in 100 g of the edible portion of 547 seafood species. Note the x-axis is plotted on a log scale. (Lower) Proportion of species, and number shown on each bar, with available data that reach 10% of RDA targets for any one, two, or up to five of the micronutrients and fatty acids examined here.

Fig. 3.

Aquatic biodiversity enhances nutritional benefits. (A) Seafood species richness improves the efficiency with which human diets can meet RDA targets by reducing the minimum portion size required, P_min, to meet RDA targets (measured in grams of seafood). P_min is shown for micronutrients, fatty acids, and protein separately (points are median values for calcium, iron, zinc, EPA, DHA, and protein, lines show the fit of Eq. 3 to the data, and shading refers to 95% CI) as well as for the five micronutrients and fatty acids simultaneously (top purple line). Colors corresponding to each nutrient in A are shown in B. (B) Estimates (± 95% CI) for the scaling parameter that relates species richness to P_min (b_Pmin) (Eq. 3). (C) Species richness increases the number of distinct nutrient RDA targets met in a 100 g seafood portion (NT); black line and 95% CI correspond to the fit of Eq. 2 to mean NT derived from resampled diets from the global seafood species pool. Flower plots in C summarize the micronutrient and fatty acid concentrations relative to 10% RDA (gray circle) in two representative diets at low and high species richness levels. Data shown in A and C are derived from n = 1,000 resampled diets.

Fig. 4.

Frequency histograms of concentration of arsenic (A), cadmium (B), lead (C), and methylmercury (D) in edible muscle tissues of North American aquatic species relative to PTDI. (E) Increasing seafood species richness increases the number of contaminants which exceed the upper tolerable limit (PTDI) in a 100 g portion (NC). Black line indicates the mean NC from 1,000 bootstrapped samples of seafood diets sampled from the North American seafood contaminant dataset, and gray shading refers to 95% CIs. Slope, b_NC = 0.10, 95% CI 0.084, 0.12.

Fig. 5.

Nutrient concentrations in finfish muscle tissue vary with ecological traits in ways that differ among the essential trace elements (calcium, iron, zinc) and the essential fatty acids (EPA and DHA). Model-averaged standardized regression coefficients and 95% CIs from phylogenetic least squares regression (see SI Appendix, Methods 4 for full model description) are shown for samples including muscle or muscle and skin tissues only. Traits for which there is no symbol did not appear in any of the models in the top 95% set (with cumulative sum of Akaike weights ≤ 0.95). Open symbols indicate coefficient estimates for which 95% CIs do not encompass zero. Note that x-axes differ across panels for clarity of presentation. Number of species: n = 155 for EPA, n = 159 for DHA, n = 104 for calcium, n = 99 for iron, and n = 90 for zinc. For model results including tissues other than muscle tissue, see SI Appendix, Tables S4–S11.

Fig. 6.

(A) Ecological functional diversity, EFD, captures variation in the ecological traits and ecological roles of species and can be quantified as the average of the distances between species’ trait values (circles) and the center of functional trait space (square, indicated by z, adapted from ref. 93). (B) Seafood diets with higher levels of EFD are associated with higher levels of nutritional benefits (i.e., higher number of RDA targets per 100 g portion). Probability of reaching five micronutrient and fatty acid RDA targets simultaneously in a single 100 g portion (NT = 5, light orange line) increases as the EFD of the diet increases. Probabilities predicted from ordinal logistic regression (log odds of functional diversity = 2.08, 95% CI [0.52, 3.64], n = 1,000 resampled diets).