scholarly journals Large-scale shift in the structure of a kelp forest ecosystem co-occurs with an epizootic and marine heatwave

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Meredith L. McPherson ◽  
Dennis J. I. Finger ◽  
Henry F. Houskeeper ◽  
Tom W. Bell ◽  
Mark H. Carr ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Large Scale ◽  
Nutrient Dynamics ◽  
Sea Urchins ◽  
Management Strategies ◽  
Kelp Forest ◽  
Kelp Forests ◽  
Predator Population ◽  
Northern California ◽  
Boundary Current

AbstractClimate change is responsible for increased frequency, intensity, and duration of extreme events, such as marine heatwaves (MHWs). Within eastern boundary current systems, MHWs have profound impacts on temperature-nutrient dynamics that drive primary productivity. Bull kelp (Nereocystis luetkeana) forests, a vital nearshore habitat, experienced unprecedented losses along 350 km of coastline in northern California beginning in 2014 and continuing through 2019. These losses have had devastating consequences to northern California communities, economies, and fisheries. Using a suite of in situ and satellite-derived data, we demonstrate that the abrupt ecosystem shift initiated by a multi-year MHW was preceded by declines in keystone predator population densities. We show strong evidence that northern California kelp forests, while temporally dynamic, were historically resilient to fluctuating environmental conditions, even in the absence of key top predators, but that a series of coupled environmental and biological shifts between 2014 and 2016 resulted in the formation of a persistent, altered ecosystem state with low primary productivity. Based on our findings, we recommend the implementation of ecosystem-based and adaptive management strategies, such as (1) monitoring the status of key ecosystem attributes: kelp distribution and abundance, and densities of sea urchins and their predators, (2) developing management responses to threshold levels of these attributes, and (3) creating quantitative restoration suitability indices for informing kelp restoration efforts.

Dynamic phosphorus mass balance modeling of large watersheds: long-term implications of management strategies

2001 ◽  
Vol 43 (5) ◽  
pp. 153-162 ◽  
Author(s):  
E. A. Cassell ◽  
R. L. Kort ◽  
D. W. Meals ◽  
S. G. Aschmann ◽  
J. M. Dorioz ◽  
...  
Keyword(s):  
Mass Balance ◽  
Urban Growth ◽  
Large Scale ◽  
Nutrient Dynamics ◽  
Agricultural Soils ◽  
Management Strategies ◽  
Wastewater Management ◽  
Long Term Effects ◽  
Modeling Process

The principles of mass balance, compartment-flux diagramming, and dynamic simulation modeling are integrated to create computer models that estimate phosphorus (P) export from large-scale watersheds over long-term futures. These Watershed Ecosystem Nutrient Dynamics (WEND) models are applied to a 275,000 ha dairy-documented watershed and a 77,000 ha poultry-dominated watershed in northeastern USA. Model predictions of present-day P export loads are consistent with monitoring data and estimates made using P export coefficients. For both watersheds P import exceeds P export and P is accumulating in the agricultural soils. Agricultural and urban activities are major contributors to P export from both watersheds. Continued urban growth will increase P export over time unless wastewater management is substantially enhanced and/or rates of urban growth are controlled. Agriculture cannot rely solely on the implementation of increasingly stringent conservation practices to reduce long-term P export but mustconsider options that promote P input/output balance. The WEND modeling process is a powerful tool to integrate the diversity of activities in watersheds into a holistic framework. Model outputs are suited to assist managers to explore long-term effects of overall watershed management strategies on P export in comparison to environmental and economic goals.

scholarly journals The sea urchin – the ultimate herbivore and biogeographic variability in its ability to deforest kelp ecosystems

2013 ◽  
Author(s):  
Jarrett E Byrnes ◽  
Ladd E. Johnson ◽  
Sean D. Connell ◽  
Nick T. Shears ◽  
Selena M McMillan ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Large Scale ◽  
Sea Urchins ◽  
Meta Analysis ◽  
Kelp Forest ◽  
Rocky Reef ◽  
Rocky Reefs ◽  
Iconic Images ◽  
Balance Of Forces ◽  
Almost All

Barren rocky seafloor landscapes, denuded of almost all life by ravenous sea urchins, liberated from their predators, stands as one of the iconic images of trophic cascades in Ecology. While this paradigm has been cited in nearly every temperate rocky reef ecosystem across the globe, there is widespread disagreement as to its generality. Given their biology, sea urchins are clearly one of the ocean’s strongest herbivores in many systems, but where will their impact be strongest? Here we perform a global meta-analysis of sea urchin-kelp relationships in the field. We find that sea urchins appear to be able to control kelp abundances in any system where they can achieve high densities. Furthermore, their ability to create large-scale long-lasting barrens appears to be limited to biogeographic regions where they can achieve high consumptive potential. Based on the literature, we outline a conceptual model that examines when and where sea urchins should be able to have a strong regulating impact on kelp forest ecosystems. We suggest that many elements of global change may shift the balance of forces regulating sea urchin consumptive potential in these ecosystems. Given their ability to have strong impacts on temperate rocky reefs, these drivers need to be considered in concert with their effect on sea urchins when attempting to predict future change to marine ecosystems.

scholarly journals Zombies of the nearshore: Metabolic depression in sea urchin barrens associated with food deprivation

2020 ◽  
Author(s):  
Nathan B. Spindel ◽  
Lynn C. Lee ◽  
Daniel K. Okamoto
Keyword(s):  
Body Mass ◽  
Food Deprivation ◽  
Microbial Mats ◽  
Sea Urchins ◽  
Kelp Forest ◽  
Resource Limitation ◽  
Kelp Forests ◽  
Metabolic Rates ◽  
Energy Reserves ◽  
Study Sites

AbstractThe proliferation of sea urchins can decimate macroalgal forests in coastal ecosystems, leading to persistent barren seascapes. While kelp forests are among the most productive ecosystems on the planet, productivity in these urchin barrens is dramatically reduced. Moreover, urchins inhabiting these food-depauperate barrens face starvation and many survive in these barrens for years or decades. Urchins in barrens can persist by eating food subsidies from drift algae, pelagic salps, tubeworms, as well as encrusting and filamentous algae, microbial mats, and slow-growing species resistant to herbivory. Despite both food from endogenous production and exogenous subsidies, many urchins in barrens likely experience prolonged food deprivation. This resource limitation may create a trade-off between reproduction and survival; for example, fecundity of purple sea urchins (Strongylocentrotus purpuratus) is 99.9% lower in barrens. Despite food constraints, red sea urchins (Mesocentrotus franciscanus), the dominant urchin species at our study sites, can live in excess of 100 years and barrens in Haida Gwaii, British Columbia (BC), Canada, have persisted for at least 143 years. While these phenomena are widespread and well documented, the bioenergetic adaptations that allow urchins to persist in these food-depauperate barrens remain poorly understood. To quantify habitat-specific differences in metabolic rates and energy reserves (as measured by gonadal mass), we conducted respirometry on and measured gonadal mass in M. franciscanus at three locations in BC inside and outside of adjacent kelp forest and barrens habitat. Here we demonstrate that M. franciscanus in barrens versus kelp forests have substantially lower energy reserves and, importantly, also exhibit dramatic reductions in size-specific resting metabolic rates (RMR), even after standardizing by metabolically active body mass. On average, gonadal mass was 44.6% lower and RMR scaled to metabolically active body mass was 40% lower in barrens urchins than in kelp forest urchins. Such a shift in metabolic rate may provide a mechanism that facilitates barren state stability over long time scales as M. franciscanus can lower energetic demands while they wait for small pulses of food, scrape by on low-productivity resources, and suppress recruitment of macroalgae for months, years, or decades.

scholarly journals The sea urchin – the ultimate herbivore and biogeographic variability in its ability to deforest kelp ecosystems

2013 ◽  
Author(s):  
Jarrett E Byrnes ◽  
Ladd E. Johnson ◽  
Sean D. Connell ◽  
Nick T. Shears ◽  
Selena M McMillan ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Large Scale ◽  
Sea Urchins ◽  
Meta Analysis ◽  
Kelp Forest ◽  
Rocky Reef ◽  
Rocky Reefs ◽  
Iconic Images ◽  
Balance Of Forces ◽  
Almost All

Barren rocky seafloor landscapes, denuded of almost all life by ravenous sea urchins, liberated from their predators, stands as one of the iconic images of trophic cascades in Ecology. While this paradigm has been cited in nearly every temperate rocky reef ecosystem across the globe, there is widespread disagreement as to its generality. Given their biology, sea urchins are clearly one of the ocean’s strongest herbivores in many systems, but where will their impact be strongest? Here we perform a global meta-analysis of sea urchin-kelp relationships in the field. We find that sea urchins appear to be able to control kelp abundances in any system where they can achieve high densities. Furthermore, their ability to create large-scale long-lasting barrens appears to be limited to biogeographic regions where they can achieve high consumptive potential. Based on the literature, we outline a conceptual model that examines when and where sea urchins should be able to have a strong regulating impact on kelp forest ecosystems. We suggest that many elements of global change may shift the balance of forces regulating sea urchin consumptive potential in these ecosystems. Given their ability to have strong impacts on temperate rocky reefs, these drivers need to be considered in concert with their effect on sea urchins when attempting to predict future change to marine ecosystems.

scholarly journals Energetic context determines the effects of multiple upwelling-associated stressors on sea urchin performance

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kindall A. Murie ◽  
Paul E. Bourdeau
Keyword(s):  
Coastal Upwelling ◽  
Multiple Stressors ◽  
Sea Urchins ◽  
Strongylocentrotus Purpuratus ◽  
Kelp Forest ◽  
Low Ph ◽  
Kelp Forests ◽  
Distant Future ◽  
Urchin Barren ◽  
Insight Into

AbstractGlobally, kelp forests are threatened by multiple stressors, including increasing grazing by sea urchins. With coastal upwelling predicted to increase in intensity and duration in the future, understanding whether kelp forest and urchin barren urchins are differentially affected by upwelling-related stressors will give insight into how future conditions may affect the transition between kelp forests and barrens. We assessed how current and future-predicted changes in the duration and magnitude of upwelling-associated stressors (low pH, dissolved oxygen, and temperature) affected the performance of purple sea urchins (Strongylocentrotus purpuratus) sourced from rapidly-declining bull kelp (Nereocystis leutkeana) forests and nearby barrens and maintained on habitat-specific diets. Kelp forest urchins were of superior condition to barrens urchins, with ~ 6–9 times more gonad per body mass. Grazing and condition in kelp forest urchins were more negatively affected by distant-future and extreme upwelling conditions, whereas grazing and survival in urchins from barrens were sensitive to both current-day and all future-predicted upwelling, and to increases in acidity, hypoxia, and temperature regardless of upwelling. We conclude that urchin barren urchins are more susceptible to increases in the magnitude and duration of upwelling-related stressors than kelp forest urchins. These findings have important implications for urchin population dynamics and their interaction with kelp.

scholarly journals Ecological performance differs between range centre and trailing edge populations of a cold-water kelp: implications for estimating net primary productivity

2020 ◽  
Vol 167 (9) ◽  
Author(s):  
Nathan G. King ◽  
Pippa J. Moore ◽  
Albert Pessarrodona ◽  
Michael T. Burrows ◽  
Joanne Porter ◽  
...  
Keyword(s):  
Carbon Cycling ◽  
Primary Productivity ◽  
Large Scale ◽  
Net Primary Productivity ◽  
Cold Water ◽  
Standing Stock ◽  
Kelp Forests ◽  
Growth Season ◽  
Trailing Edge ◽  
Carbon Cycles

Abstract Kelp forests are extensive, widely distributed and highly productive. However, despite their importance, reliable estimates of net primary productivity (NPP) are currently unknown for most species and regions. In particular, how performance and subsequent NPP change throughout a species range is lacking. Here, we attempted to resolve this by examining growth and performance of the boreal kelp, Laminaria digitata, from range centre and trailing edge regions in the United Kingdom. During the peak growth season (March/April), range-centre individuals were up to three times heavier and accumulated biomass twice as fast as their trailing-edge counterparts. This was not apparent during the reduced growth season (August/September), when populations within both regions had similar biomass profiles. In total, annual NPP estimates were considerably lower for trailing-edge (181 ± 34 g C m−2 year−1) compared to range-centre (344 ± 33 g C m−2 year−1) populations. Our first-order UK estimates of total standing stock and NPP for L. digitata suggest this species makes a significant contribution to coastal carbon cycling. Further work determining the ultimate fate of this organic matter is needed to understand the overall contribution of kelp populations to regional and global carbon cycles. Nevertheless, we highlight the need for large-scale sampling across multiple populations and latitudes to accurately evaluate kelp species’ contributions to coastal carbon cycling.

scholarly journals Sea urchins mediate the availability of kelp detritus to benthic consumers

2019 ◽  
Vol 286 (1906) ◽  
pp. 20190846 ◽  
Author(s):  
Christie E. Yorke ◽  
Henry M. Page ◽  
Robert J. Miller
Keyword(s):  
Food Webs ◽  
Sea Urchins ◽  
Strongylocentrotus Purpuratus ◽  
Kelp Forest ◽  
Macrocystis Pyrifera ◽  
Mesocosm Experiment ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Trophic Role ◽  
Benthic Consumers

Detritus can fundamentally shape and sustain food webs, and shredders can facilitate its availability. Most of the biomass of the highly productive giant kelp, Macrocystis pyrifera , becomes detritus that is exported or falls to the seafloor as litter. We hypothesized that sea urchins process kelp litter through shredding, sloppy feeding and egestion, making kelp litter more available to benthic consumers. To test this, we conducted a mesocosm experiment in which an array of kelp forest benthic consumers were exposed to 13 C- and 15 N-labelled Macrocystis with or without the presence of sea urchins, Strongylocentrotus purpuratus . Our results showed that several detritivore species consumed significant amounts of kelp, but only when urchins were present. Although they are typically portrayed as antagonistic grazers in kelp forests, sea urchins can have a positive trophic role, capturing kelp litter before it is exported and making it available to a suite of benthic detritivores.

scholarly journals Long photoperiods sustain high pH in Arctic kelp forests

2016 ◽  
Vol 2 (12) ◽  
pp. e1501938 ◽  
Author(s):  
Dorte Krause-Jensen ◽  
Núria Marbà ◽  
Marina Sanz-Martin ◽  
Iris E. Hendriks ◽  
Jakob Thyrring ◽  
...  
Keyword(s):  
Gradual Increase ◽  
Sea Urchins ◽  
Kelp Forest ◽  
Kelp Forests ◽  
Arctic Vegetation ◽  
Seagrass Meadows ◽  
Potential Benefits ◽  
Ph Increase

Concern on the impacts of ocean acidification on calcifiers, such as bivalves, sea urchins, and foraminifers, has led to efforts to understand the controls on pH in their habitats, which include kelp forests and seagrass meadows. The metabolism of these habitats can lead to diel fluctuation in pH with increases during the day and declines at night, suggesting no net effect on pH at time scales longer than daily. We examined the capacity of subarctic and Arctic kelps to up-regulate pH in situ and experimentally tested the role of photoperiod in determining the capacity of Arctic macrophytes to up-regulate pH. Field observations at photoperiods of 15 and 24 hours in Greenland combined with experimental manipulations of photoperiod show that photoperiods longer than 21 hours, characteristic of Arctic summers, are conducive to sustained up-regulation of pH by kelp photosynthesis. We report a gradual increase in pH of 0.15 units and a parallel decline in pCO2of 100 parts per million over a 10-day period in an Arctic kelp forest over midsummer, with ample scope for continued pH increase during the months of continuous daylight. Experimental increase in CO2concentration further stimulated the capacity of macrophytes to deplete CO2and increase pH. We conclude that long photoperiods in Arctic summers support sustained up-regulation of pH in kelp forests, with potential benefits for calcifiers, and propose that this mechanism may increase with the projected expansion of Arctic vegetation in response to warming and loss of sea ice.

scholarly journals Coastal fish assemblages and predation pressure in northern-central Chilean Lessonia trabeculata kelp forests and barren grounds

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6964 ◽  
Author(s):  
Nicolás Riquelme-Pérez ◽  
Catalina A. Musrri ◽  
Wolfgang B. Stotz ◽  
Osvaldo Cerda ◽  
Oscar Pino-Olivares ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Sea Urchins ◽  
Kelp Forest ◽  
Predation Pressure ◽  
Predatory Fish ◽  
The Black Sea ◽  
Kelp Forests ◽  
Fishing Activity ◽  
Rocky Habitats ◽  
Barren Grounds

Kelp forests are declining in many parts of the globe, which can lead to the spreading of barren grounds. Increased abundances of grazers, mainly due to reduction of their predators, are among the causes of this development. Here, we compared the species richness (SR), frequency of occurrence (FO), and maximum abundance (MaxN) of predatory fish and their predation pressure between kelp forest and barren ground habitats of northern-central Chile. Sampling was done using baited underwater cameras with vertical and horizontal orientation. Two prey organisms were used as tethered baits, the black sea urchin Tetrapygus niger and the porcelanid crab Petrolisthes laevigatus. SR did not show major differences between habitats, while FO and MaxN were higher on barren grounds in vertical videos, with no major differences between habitats in horizontal videos. Predation pressure did not differ between habitats, but after 24 h consumption of porcelanid crabs was significantly higher than that of sea urchins. Scartichthys viridis/gigas was the main predator, accounting for 82% of the observed predation events on Petrolisthes laevigatus. Most of these attacks occurred on barren grounds. Scartichthys viridis/gigas was the only fish observed attacking (but not consuming) tethered sea urchins. High abundances of opportunistic predators (Scartichthys viridis/gigas) are probably related to low abundances of large predatory fishes. These results suggest that intense fishing activity on large predators, and their resulting low abundances, could result in low predation pressure on sea urchins, thereby contributing to the increase of T. niger abundances in subtidal rocky habitats.

scholarly journals Trophic downgrading reduces spatial variability on rocky reefs

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Matthew S. Edwards ◽  
Brenda Konar
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Kelp Forest ◽  
Small Scale ◽  
Kelp Forests ◽  
Forest Communities ◽  
Opposite Pattern ◽  
Rocky Reefs ◽  
Urchin Barren ◽  
Sea Urchin Barrens

Abstract Trophic downgrading in coastal waters has occurred globally during recent decades. On temperate rocky reefs, this has resulted in widespread kelp deforestation and the formation of sea urchin barrens. We hypothesize that the intact kelp forest communities are more spatially variable than the downgraded urchin barren communities, and that these differences are greatest at small spatial scales where the influence of competitive and trophic interactions is strongest. To address this, benthic community surveys were done in kelp forests and urchin barrens at nine islands spanning 1230 km of the Aleutian Archipelago where the loss of predatory sea otters has resulted in the trophic downgrading of the region’s kelp forests. We found more species and greater total spatial variation in community composition within the kelp forests than in the urchin barrens. Further, the kelp forest communities were most variable at small spatial scales (within each forest) and least variable at large spatial scales (among forests on different islands), while the urchin barren communities followed the opposite pattern. This trend was consistent for different trophic guilds (primary producers, grazers, filter feeders, predators). Together, this suggests that Aleutian kelp forests create variable habitats within their boundaries, but that the communities within these forests are generally similar across the archipelago. In contrast, urchin barrens exhibit relatively low variability within their boundaries, but these communities vary substantially among different barrens across the archipelago. We propose this represents a shift from small-scale biological control to large-scale oceanographic control of these communities.

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