Pamela Reynolds | University of California, Davis (original) (raw)

Papers by Pamela Reynolds

Limnology and Oceanography, May 26, 2021

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2012

Widespread overharvesting of top consumers of the world's ecosystems has ''skewed'' food webs, in... more Widespread overharvesting of top consumers of the world's ecosystems has ''skewed'' food webs, in terms of biomass and species richness, towards a generally greater domination at lower trophic levels. This skewing is exacerbated in locations where exotic species are predominantly low-trophic level consumers such as benthic macrophytes, detritivores, and filter feeders. However, in some systems where numerous exotic predators have been added, sometimes purposefully as in many freshwater systems, food webs are skewed in the opposite direction toward consumer dominance. Little is known about how such modifications to food web topology, e.g., changes in the ratio of predator to prey species richness, affect ecosystem functioning. We experimentally measured the effects of trophic skew on production in an estuarine food web by manipulating ratios of species richness across three trophic levels in experimental mesocosms. After 24 days, increasing macroalgal richness promoted both plant biomass and grazer abundance, although the positive effect on plant biomass disappeared in the presence of grazers. The strongest trophic cascade on the experimentally stocked macroalgae emerged in communities with a greater ratio of prey to predator richness (bottom-rich food webs), while stronger cascades on the accumulation of naturally colonizing algae (primarily microalgae with some early successional macroalgae that recruited and grew in the mesocosms) generally emerged in communities with greater predator to prey richness (the more top-rich food webs). These results suggest that trophic skewing of species richness and overall changes in food web topology can influence marine community structure and food web dynamics in complex ways, emphasizing the need for multitrophic approaches to understand the consequences of marine extinctions and invasions.

Ecological Monographs, Feb 1, 2013

Predators can influence prey population dynamics by affecting prey behaviors with strong fitness ... more Predators can influence prey population dynamics by affecting prey behaviors with strong fitness consequences, with cascading effects on lower trophic levels. Here, we demonstrate that multiple predator species can nonconsumptively influence prey population growth and the strength of a trophic cascade in a model marine community. We exposed the herbivorous amphipod Ampithoe longimana to olfactory and visual cues from three common predators (pinfish, mud crabs, brown shrimp) singly and together in a multiple-predator assemblage to quantify the nonconsumptive effects (NCEs) of predator identity and the presence of multiple predators on prey population and community-level metrics. The presence of predator cues, particularly those of the pinfish and the multiple-predator treatments, decreased prey population growth and influenced primary and secondary production. To explore mechanisms underlying the observed NCEs in the experimental communities and their potential influence in the field, we quantified individual prey behavioral responses (changes in grazing rate, diet preference, dispersal, colonization) in the presence of predator cues. Predator cues decreased prey grazing, dispersal, and colonization but did not affect prey diet preference. Given the persistence of NCEs over time and the fact that trophic cascades are common features of marine systems, changes in marine predator communities may have widespread effects on predator-prey behavioral interactions with consequences for ecosystem function even in areas of weak predation pressure.

Predators can influence prey population dynamics by affecting prey behaviors with strong fitness ... more Predators can influence prey population dynamics by affecting prey behaviors with strong fitness consequences. Here, we demonstrate that multiple predator species can nonconsumptively influence prey population growth and the strength of a trophic cascade in a model marine community. We exposed the herbivorous amphipod Ampithoe longimana to olfactory and visual cues from common predators (pinfish, mud crabs, brown shrimp) to quantify the nonconsumptive effects (NCEs) of predator identity and richness on individual, population and community level metrics. Predator cues decreased prey grazing rates, dispersal, colonization, and population growth, and influenced primary and secondary production. The presence of one intimidator, pinfish, consistently elicited strong NCEs and drove effects of predator richness. Given the persistence of NCEs over time and the fact that trophic cascades are common features of marine systems, changing marine predator diversity may have widespread effects on predator-prey behavioral interactions, with consequences for ecosystem function even in areas of weak predation pressure.

Marine Ecology Progress Series, Feb 11, 2010

Global Ecology and Biogeography

AimStudies on latitudinal patterns in plant defence have traditionally overlooked the potential e... more AimStudies on latitudinal patterns in plant defence have traditionally overlooked the potential effect that resource availability may have in shaping plant defence. Likewise, latitudinal patterns of tolerance traits have rarely been studied, yet they can be a critical component of plant defence. Therefore, the aim of our study was to examine latitudinal variation in the production of tolerance and resistance traits against herbivory along a latitudinal range and a natural gradient of resource availability from upwelling conditions.LocationNorth America (Canada, USA, Mexico).Time periodSummer months of 2015.Major taxa usedThe seagrass Zostera marina.MethodsWe conducted experiments simulating macroherbivore (e.g., bird, fish) damage on the seagrass Z. marina at 10 sites across the Eastern Pacific coast (Canada–Mexico) and Quebec and analysed several traits related to resistance and tolerance strategies against herbivory. In addition, we examined the effects of potential seagrass chang...

Proceedings of the National Academy of Sciences

Distribution of Earth’s biomes is structured by the match between climate and plant traits, which... more Distribution of Earth’s biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate–trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth’s environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass ( Zostera marina ), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more...

Proceedings of the Royal Society B: Biological Sciences

While considerable evidence exists of biogeographic patterns in the intensity of species interact... more While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass (Zostera marina) spanning 30° of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how b...

American Geophysical Union eBooks, Feb 1, 2016

The role of predation has long influenced our understanding of ecological processes from the indi... more The role of predation has long influenced our understanding of ecological processes from the individual to the landscape level. Recent interest in the role of nonconsumptive effects of predators, or the consequences of prey defensive behaviors in response to predation risk, has revolutionized how ecologists perceive the role of predators in ecological communities. From focusing on how individual predators affect prey risk taking behaviors and foraging tactics, to the consequences of these behavioral shifts for ecosystem functions and services including primary production, nutrient cycling and energy transfer, we now know that the mere presence of predators can sometimes be more important than their lethal effects on prey density. However, predicting the cascading effects of multiple predator assemblages is often challenging and counterintuitive due to the consequences of behavioral interactions among predators and their prey. I tested the effects of predator presence, identity and r...

Ecology, 2021

Human activities degrade and fragment coastal marine habitats, reducing their structural complexi... more Human activities degrade and fragment coastal marine habitats, reducing their structural complexity and making habitat edges a prevalent seascape feature. Though habitat edges frequently are implicated in reduced faunal survival and biodiversity, results of experiments on edge effects have been inconsistent, calling for a mechanistic approach to the study of edges that explicitly includes indirect and interactive effects of habitat alteration at multiple scales across biogeographic gradients. We used an experimental network spanning 17 eelgrass (Zostera marina) sites across the Atlantic and Pacific oceans and the Mediterranean Sea to determine (1) if eelgrass edges consistently increase faunal predation risk, (2) whether edge effects on predation risk are altered by habitat degradation (shoot thinning), and (3) whether variation in the strength of edge effects among sites can be explained by biogeographical variability in covarying eelgrass habitat features. Contrary to expectations...

Oikos, 2017

Form-function relationships in plants underlie their ecosystem roles in supporting higher trophic... more Form-function relationships in plants underlie their ecosystem roles in supporting higher trophic levels through primary production, detrital pathways, and habitat provision. For widespread, phenotypically-variable plants, productivity may differ not only across abiotic conditions, but also from distinct morphological or demographic traits. A single foundation species, eelgrass Zostera marina, typically dominates north temperate seagrass meadows, which we studied across 14 sites spanning 32-61°N latitude and two ocean basins. Body size varied by nearly two orders of magnitude through this range, and was largest at mid-latitudes and in the Pacific Ocean. At the global scale, neither latitude, site-level environmental conditions, nor body size helped predict productivity (relative growth rate 1-2% day-1 at most sites), suggesting a remarkable capacity of Z. marina to achieve similar productivity in summer. Furthermore, among a suite of stressors applied within sites, only ambient leaf damage reduced productivity; grazer reduction and nutrient addition had no effect on eelgrass size or growth. Scaledependence was evident in different allometric relationships within and across sites for productivity and for modules (leaf count) relative to size. Zostera marina provides a range of ecosystem functions related to both body size (habitat provision, water flow) and growth rates (food, carbon dynamics). Our observed decoupling of body size and maximum production suggests that geographic variation in these ecosystem functions may be independent, with a future need to resolve how local adaptation or plasticity of body size might actually enable more consistent peak productivity across disparate environmental conditions.

Marine Ecology Progress Series, 2019

Recent studies have shown a decline in predation intensity in seagrasses with higher latitude, bu... more Recent studies have shown a decline in predation intensity in seagrasses with higher latitude, but knowledge about arctic and subarctic regions is scarce. Moreover, changes in trophic structure are likely to vary with latitude, and to impact predation. Thus inclusion of high-latitude sites and the quantifyication of predation at multiple trophic levels are critical for our understanding of predator-prey dynamics in seagrasses at a global scale. In this in situ study, we investigated predator communities and predation rates in 2 subarctic seagrass meadows in Northern Norway. We measured the effect of seagrass density on abundances of small-bodied fish and predation rates on small (amphipods/mesograzers) and medium-sized crustaceans (shrimps/mesopredators) using a standardized live tethering technique. Results varied strongly between both study sites. Juvenile fish occurred in higher diversity and density in high seagrass density in one meadow, while sticklebacks dominated the other meadow, irrespective of habitat complexity. Predation rates varied strongly between prey type; on average, 41 % of shrimps and 16% of amphipods were consumed, while a standardized non-live prey was consumed at a rate of only 3%. In one meadow, predation on shrimp was strongly reduced (from 60% outside the meadow to 3% in high-density patches), indicating the importance of habitat complexity in reducing predation rates at this site. The results demonstrate that predation rates differ between trophic levels, and that habitat effects on predation depend on local meadow characteristics. We found that subarctic seagrass provides habitat for a diverse fish community, and specifically one meadow hosted more juveniles of commercial species compared to bare habitats.

Global Biogeochemical Cycles, 2018

Despite the importance of coastal ecosystems for the global carbon budgets, knowledge of their ca... more Despite the importance of coastal ecosystems for the global carbon budgets, knowledge of their carbon storage capacity and the factors driving variability in storage capacity is still limited. Here we provide an estimate on the magnitude and variability of carbon stocks within a widely distributed marine foundation species throughout its distribution area in temperate Northern Hemisphere. We sampled 54 eelgrass (Zostera marina) meadows, spread across eight ocean margins and 36° of latitude, to determine abiotic and biotic factors influencing organic carbon (Corg) stocks in Zostera marina sediments. The Corg stocks (integrated over 25‐cm depth) showed a large variability and ranged from 318 to 26,523 g C/m2 with an average of 2,721 g C/m2. The projected Corg stocks obtained by extrapolating over the top 1 m of sediment ranged between 23.1 and 351.7 Mg C/ha, which is in line with estimates for other seagrasses and other blue carbon ecosystems. Most of the variation in Corg stocks was ...

Frontiers in plant science, 2017

Multi-trophic conservation and management strategies may be necessary if reciprocal linkages betw... more Multi-trophic conservation and management strategies may be necessary if reciprocal linkages between primary producers and their consumers are strong. While herbivory on aquatic plants is well-studied, direct top-down control of seagrass populations has received comparatively little attention, particularly in temperate regions. Herein, we used qualitative and meta-analytic approaches to assess the scope and consequences of avian (primarily waterfowl) herbivory on temperate seagrasses of the genus . Meta-analyses revealed widespread evidence of spatio-temporal correlations between and waterfowl abundances as well as strong top-down effects of grazing on . We also documented the identity and diversity of avian species reported to consume and qualitatively assessed their potential to exert top-down control. Our results demonstrate that and their avian herbivores are ecologically linked and we suggest that bird herbivory may influence the spatial structure, composition, and functioning ...

Ecology, Jan 30, 2017

Latitudinal gradients in species interactions are widely cited as potential causes or consequence... more Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass (Zostera marina) at 48 sites across its Northern Hemisphere range, encompassing over 37(0) of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas in situ water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simple increased metabolic activity at the time of predation. This large-scale biogeographic pattern was modified by local habitat characteristics; pre...

Ecosphere, 2017

By changing ecosystem processes and altering the physical landscape, invasive ecosystem engineers... more By changing ecosystem processes and altering the physical landscape, invasive ecosystem engineers can have substantial impacts on ecosystem functions and human economies and may facilitate other non‐native species. Eradication programs in terrestrial and aquatic systems aim to reverse the impacts of invasive species and return the system to its pre‐invasion conditions. Despite an extensive focus on the impacts of both native and non‐native ecosystem engineers, the consequences of removing invasive ecosystem engineers, particularly in coastal ecosystems, are largely unknown. In this study, we quantified changes in a benthic community following the eradication of the invasive ecosystem engineer, hybrid cordgrass Spartina, in San Francisco Bay, California. We used field experimental manipulations to test for persistent effects of both aboveground and belowground structural modifications of the invasive plant on the benthic community. We found significant effects of the invasive plant m...

Trends in ecology & evolution, 2016

Ecology letters, Jan 17, 2015

Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous exper... more Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down...

Limnology and Oceanography, May 26, 2021

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2012

Widespread overharvesting of top consumers of the world's ecosystems has ''skewed'' food webs, in... more Widespread overharvesting of top consumers of the world's ecosystems has ''skewed'' food webs, in terms of biomass and species richness, towards a generally greater domination at lower trophic levels. This skewing is exacerbated in locations where exotic species are predominantly low-trophic level consumers such as benthic macrophytes, detritivores, and filter feeders. However, in some systems where numerous exotic predators have been added, sometimes purposefully as in many freshwater systems, food webs are skewed in the opposite direction toward consumer dominance. Little is known about how such modifications to food web topology, e.g., changes in the ratio of predator to prey species richness, affect ecosystem functioning. We experimentally measured the effects of trophic skew on production in an estuarine food web by manipulating ratios of species richness across three trophic levels in experimental mesocosms. After 24 days, increasing macroalgal richness promoted both plant biomass and grazer abundance, although the positive effect on plant biomass disappeared in the presence of grazers. The strongest trophic cascade on the experimentally stocked macroalgae emerged in communities with a greater ratio of prey to predator richness (bottom-rich food webs), while stronger cascades on the accumulation of naturally colonizing algae (primarily microalgae with some early successional macroalgae that recruited and grew in the mesocosms) generally emerged in communities with greater predator to prey richness (the more top-rich food webs). These results suggest that trophic skewing of species richness and overall changes in food web topology can influence marine community structure and food web dynamics in complex ways, emphasizing the need for multitrophic approaches to understand the consequences of marine extinctions and invasions.

Ecological Monographs, Feb 1, 2013

Predators can influence prey population dynamics by affecting prey behaviors with strong fitness ... more Predators can influence prey population dynamics by affecting prey behaviors with strong fitness consequences, with cascading effects on lower trophic levels. Here, we demonstrate that multiple predator species can nonconsumptively influence prey population growth and the strength of a trophic cascade in a model marine community. We exposed the herbivorous amphipod Ampithoe longimana to olfactory and visual cues from three common predators (pinfish, mud crabs, brown shrimp) singly and together in a multiple-predator assemblage to quantify the nonconsumptive effects (NCEs) of predator identity and the presence of multiple predators on prey population and community-level metrics. The presence of predator cues, particularly those of the pinfish and the multiple-predator treatments, decreased prey population growth and influenced primary and secondary production. To explore mechanisms underlying the observed NCEs in the experimental communities and their potential influence in the field, we quantified individual prey behavioral responses (changes in grazing rate, diet preference, dispersal, colonization) in the presence of predator cues. Predator cues decreased prey grazing, dispersal, and colonization but did not affect prey diet preference. Given the persistence of NCEs over time and the fact that trophic cascades are common features of marine systems, changes in marine predator communities may have widespread effects on predator-prey behavioral interactions with consequences for ecosystem function even in areas of weak predation pressure.

Predators can influence prey population dynamics by affecting prey behaviors with strong fitness ... more Predators can influence prey population dynamics by affecting prey behaviors with strong fitness consequences. Here, we demonstrate that multiple predator species can nonconsumptively influence prey population growth and the strength of a trophic cascade in a model marine community. We exposed the herbivorous amphipod Ampithoe longimana to olfactory and visual cues from common predators (pinfish, mud crabs, brown shrimp) to quantify the nonconsumptive effects (NCEs) of predator identity and richness on individual, population and community level metrics. Predator cues decreased prey grazing rates, dispersal, colonization, and population growth, and influenced primary and secondary production. The presence of one intimidator, pinfish, consistently elicited strong NCEs and drove effects of predator richness. Given the persistence of NCEs over time and the fact that trophic cascades are common features of marine systems, changing marine predator diversity may have widespread effects on predator-prey behavioral interactions, with consequences for ecosystem function even in areas of weak predation pressure.

Marine Ecology Progress Series, Feb 11, 2010

Global Ecology and Biogeography

AimStudies on latitudinal patterns in plant defence have traditionally overlooked the potential e... more AimStudies on latitudinal patterns in plant defence have traditionally overlooked the potential effect that resource availability may have in shaping plant defence. Likewise, latitudinal patterns of tolerance traits have rarely been studied, yet they can be a critical component of plant defence. Therefore, the aim of our study was to examine latitudinal variation in the production of tolerance and resistance traits against herbivory along a latitudinal range and a natural gradient of resource availability from upwelling conditions.LocationNorth America (Canada, USA, Mexico).Time periodSummer months of 2015.Major taxa usedThe seagrass Zostera marina.MethodsWe conducted experiments simulating macroherbivore (e.g., bird, fish) damage on the seagrass Z. marina at 10 sites across the Eastern Pacific coast (Canada–Mexico) and Quebec and analysed several traits related to resistance and tolerance strategies against herbivory. In addition, we examined the effects of potential seagrass chang...

Proceedings of the National Academy of Sciences

Distribution of Earth’s biomes is structured by the match between climate and plant traits, which... more Distribution of Earth’s biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate–trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth’s environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass ( Zostera marina ), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more...

Proceedings of the Royal Society B: Biological Sciences

While considerable evidence exists of biogeographic patterns in the intensity of species interact... more While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass (Zostera marina) spanning 30° of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how b...

American Geophysical Union eBooks, Feb 1, 2016

The role of predation has long influenced our understanding of ecological processes from the indi... more The role of predation has long influenced our understanding of ecological processes from the individual to the landscape level. Recent interest in the role of nonconsumptive effects of predators, or the consequences of prey defensive behaviors in response to predation risk, has revolutionized how ecologists perceive the role of predators in ecological communities. From focusing on how individual predators affect prey risk taking behaviors and foraging tactics, to the consequences of these behavioral shifts for ecosystem functions and services including primary production, nutrient cycling and energy transfer, we now know that the mere presence of predators can sometimes be more important than their lethal effects on prey density. However, predicting the cascading effects of multiple predator assemblages is often challenging and counterintuitive due to the consequences of behavioral interactions among predators and their prey. I tested the effects of predator presence, identity and r...

Ecology, 2021

Human activities degrade and fragment coastal marine habitats, reducing their structural complexi... more Human activities degrade and fragment coastal marine habitats, reducing their structural complexity and making habitat edges a prevalent seascape feature. Though habitat edges frequently are implicated in reduced faunal survival and biodiversity, results of experiments on edge effects have been inconsistent, calling for a mechanistic approach to the study of edges that explicitly includes indirect and interactive effects of habitat alteration at multiple scales across biogeographic gradients. We used an experimental network spanning 17 eelgrass (Zostera marina) sites across the Atlantic and Pacific oceans and the Mediterranean Sea to determine (1) if eelgrass edges consistently increase faunal predation risk, (2) whether edge effects on predation risk are altered by habitat degradation (shoot thinning), and (3) whether variation in the strength of edge effects among sites can be explained by biogeographical variability in covarying eelgrass habitat features. Contrary to expectations...

Oikos, 2017

Form-function relationships in plants underlie their ecosystem roles in supporting higher trophic... more Form-function relationships in plants underlie their ecosystem roles in supporting higher trophic levels through primary production, detrital pathways, and habitat provision. For widespread, phenotypically-variable plants, productivity may differ not only across abiotic conditions, but also from distinct morphological or demographic traits. A single foundation species, eelgrass Zostera marina, typically dominates north temperate seagrass meadows, which we studied across 14 sites spanning 32-61°N latitude and two ocean basins. Body size varied by nearly two orders of magnitude through this range, and was largest at mid-latitudes and in the Pacific Ocean. At the global scale, neither latitude, site-level environmental conditions, nor body size helped predict productivity (relative growth rate 1-2% day-1 at most sites), suggesting a remarkable capacity of Z. marina to achieve similar productivity in summer. Furthermore, among a suite of stressors applied within sites, only ambient leaf damage reduced productivity; grazer reduction and nutrient addition had no effect on eelgrass size or growth. Scaledependence was evident in different allometric relationships within and across sites for productivity and for modules (leaf count) relative to size. Zostera marina provides a range of ecosystem functions related to both body size (habitat provision, water flow) and growth rates (food, carbon dynamics). Our observed decoupling of body size and maximum production suggests that geographic variation in these ecosystem functions may be independent, with a future need to resolve how local adaptation or plasticity of body size might actually enable more consistent peak productivity across disparate environmental conditions.

Marine Ecology Progress Series, 2019

Recent studies have shown a decline in predation intensity in seagrasses with higher latitude, bu... more Recent studies have shown a decline in predation intensity in seagrasses with higher latitude, but knowledge about arctic and subarctic regions is scarce. Moreover, changes in trophic structure are likely to vary with latitude, and to impact predation. Thus inclusion of high-latitude sites and the quantifyication of predation at multiple trophic levels are critical for our understanding of predator-prey dynamics in seagrasses at a global scale. In this in situ study, we investigated predator communities and predation rates in 2 subarctic seagrass meadows in Northern Norway. We measured the effect of seagrass density on abundances of small-bodied fish and predation rates on small (amphipods/mesograzers) and medium-sized crustaceans (shrimps/mesopredators) using a standardized live tethering technique. Results varied strongly between both study sites. Juvenile fish occurred in higher diversity and density in high seagrass density in one meadow, while sticklebacks dominated the other meadow, irrespective of habitat complexity. Predation rates varied strongly between prey type; on average, 41 % of shrimps and 16% of amphipods were consumed, while a standardized non-live prey was consumed at a rate of only 3%. In one meadow, predation on shrimp was strongly reduced (from 60% outside the meadow to 3% in high-density patches), indicating the importance of habitat complexity in reducing predation rates at this site. The results demonstrate that predation rates differ between trophic levels, and that habitat effects on predation depend on local meadow characteristics. We found that subarctic seagrass provides habitat for a diverse fish community, and specifically one meadow hosted more juveniles of commercial species compared to bare habitats.

Global Biogeochemical Cycles, 2018

Despite the importance of coastal ecosystems for the global carbon budgets, knowledge of their ca... more Despite the importance of coastal ecosystems for the global carbon budgets, knowledge of their carbon storage capacity and the factors driving variability in storage capacity is still limited. Here we provide an estimate on the magnitude and variability of carbon stocks within a widely distributed marine foundation species throughout its distribution area in temperate Northern Hemisphere. We sampled 54 eelgrass (Zostera marina) meadows, spread across eight ocean margins and 36° of latitude, to determine abiotic and biotic factors influencing organic carbon (Corg) stocks in Zostera marina sediments. The Corg stocks (integrated over 25‐cm depth) showed a large variability and ranged from 318 to 26,523 g C/m2 with an average of 2,721 g C/m2. The projected Corg stocks obtained by extrapolating over the top 1 m of sediment ranged between 23.1 and 351.7 Mg C/ha, which is in line with estimates for other seagrasses and other blue carbon ecosystems. Most of the variation in Corg stocks was ...

Frontiers in plant science, 2017

Multi-trophic conservation and management strategies may be necessary if reciprocal linkages betw... more Multi-trophic conservation and management strategies may be necessary if reciprocal linkages between primary producers and their consumers are strong. While herbivory on aquatic plants is well-studied, direct top-down control of seagrass populations has received comparatively little attention, particularly in temperate regions. Herein, we used qualitative and meta-analytic approaches to assess the scope and consequences of avian (primarily waterfowl) herbivory on temperate seagrasses of the genus . Meta-analyses revealed widespread evidence of spatio-temporal correlations between and waterfowl abundances as well as strong top-down effects of grazing on . We also documented the identity and diversity of avian species reported to consume and qualitatively assessed their potential to exert top-down control. Our results demonstrate that and their avian herbivores are ecologically linked and we suggest that bird herbivory may influence the spatial structure, composition, and functioning ...

Ecology, Jan 30, 2017

Latitudinal gradients in species interactions are widely cited as potential causes or consequence... more Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass (Zostera marina) at 48 sites across its Northern Hemisphere range, encompassing over 37(0) of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas in situ water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simple increased metabolic activity at the time of predation. This large-scale biogeographic pattern was modified by local habitat characteristics; pre...

Ecosphere, 2017

By changing ecosystem processes and altering the physical landscape, invasive ecosystem engineers... more By changing ecosystem processes and altering the physical landscape, invasive ecosystem engineers can have substantial impacts on ecosystem functions and human economies and may facilitate other non‐native species. Eradication programs in terrestrial and aquatic systems aim to reverse the impacts of invasive species and return the system to its pre‐invasion conditions. Despite an extensive focus on the impacts of both native and non‐native ecosystem engineers, the consequences of removing invasive ecosystem engineers, particularly in coastal ecosystems, are largely unknown. In this study, we quantified changes in a benthic community following the eradication of the invasive ecosystem engineer, hybrid cordgrass Spartina, in San Francisco Bay, California. We used field experimental manipulations to test for persistent effects of both aboveground and belowground structural modifications of the invasive plant on the benthic community. We found significant effects of the invasive plant m...

Trends in ecology & evolution, 2016

Ecology letters, Jan 17, 2015

Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous exper... more Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down...