scholarly journals Balancing exploitation and conservation of the eastern Scotian Shelf ecosystem: application of a 4D ecosystem exploitation index

2005 ◽  
Vol 62 (3) ◽  
pp. 503-510 ◽  
Author(s):  
Alida Bundy ◽  
Paul Fanning ◽  
Kees C.T. Zwanenburg
Keyword(s):  
Species Richness ◽  
Trophic Structure ◽  
Trophic Levels ◽  
Scotian Shelf ◽  
Central Concept ◽  
Model Simulations ◽  
Lag Effects ◽  
Ecosystem Level ◽  
Cross System ◽  
Exploitation Index

Abstract Few indicators exist that measure the effects of fishing at the whole-ecosystem level. A 4D ecosystem exploitation index is proposed that integrates four measures of ecosystem status: (i) the trophic balance of exploitation, (ii) the intensity of exploitation, (iii) species richness, and (iv) disturbance of the trophic structure. The central concept is that fisheries should extract yield in proportion to the productivity at each trophic level, at sustainable exploitation rates, with minimal disturbance to the trophic structure, and with no loss in species richness. The ecosystem exploitation index is tested on simulated ecosystem data and applied to data from the eastern Scotian Shelf, Canada. The model simulations provided consistent results that should facilitate cross-system comparisons of exploitation and ecosystem status. When applied to actual observations, the results were less coherent, likely attributable to lag effects and environmental impacts. All fisheries likely alter the trophic structure of ecosystems, and the rate and trophic pattern of exploitation determines the level of change. Exploiting all trophic levels equally would always result in less change to trophic structure than top-heavy exploitation. Further testing is required to determine lag effects and sensitivity to various assumptions.

scholarly journals The importance of sponges and mangroves in supporting fish communities on degraded coral reefs in Caribbean Panama

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4455 ◽  
Author(s):  
Janina Seemann ◽  
Alexandra Yingst ◽  
Rick D. Stuart-Smith ◽  
Graham J. Edgar ◽  
Andrew H. Altieri
Keyword(s):  
Species Richness ◽  
Coral Reefs ◽  
Trophic Structure ◽  
Small Body ◽  
Fish Communities ◽  
Trophic Levels ◽  
Fish Biomass ◽  
Seagrass Meadows ◽  
Total Fish ◽  
The Caribbean

Fish communities associated with coral reefs worldwide are threatened by habitat degradation and overexploitation. We assessed coral reefs, mangrove fringes, and seagrass meadows on the Caribbean coast of Panama to explore the influences of their proximity to one another, habitat cover, and environmental characteristics in sustaining biomass, species richness and trophic structure of fish communities in a degraded tropical ecosystem. We found 94% of all fish across all habitat types were of small body size (≤10 cm), with communities dominated by fishes that usually live in habitats of low complexity, such as Pomacentridae (damselfishes) and Gobiidae (gobies). Total fish biomass was very low, with the trend of small fishes from low trophic levels over-represented, and top predators under-represented, relative to coral reefs elsewhere in the Caribbean. For example, herbivorous fishes comprised 27% of total fish biomass in Panama relative to 10% in the wider Caribbean, and the small parrotfishScarus isericomprised 72% of the parrotfish biomass. We found evidence that non-coral biogenic habitats support reef-associated fish communities. In particular, the abundance of sponges on a given reef and proximity of mangroves were found to be important positive correlates of reef fish species richness, biomass, abundance and trophic structure. Our study indicates that a diverse fish community can persist on degraded coral reefs, and that the availability and arrangement within the seascape of other habitat-forming organisms, including sponges and mangroves, is critical to the maintenance of functional processes in such ecosystems.

scholarly journals Stand age and species richness dampen interannual variation of ecosystem-level photosynthetic capacity

2017 ◽  
Vol 1 (2) ◽  
Author(s):  
Talie Musavi ◽  
Mirco Migliavacca ◽  
Markus Reichstein ◽  
Jens Kattge ◽  
Christian Wirth ◽  
...  
Keyword(s):  
Species Richness ◽  
Interannual Variation ◽  
Photosynthetic Capacity ◽  
Stand Age ◽  
Ecosystem Level

scholarly journals Aboveground impacts of a belowground invader: how invasive earthworms alter aboveground arthropod communities in a northern North American forest

2021 ◽  
Author(s):  
Malte Jochum ◽  
Lise Thouvenot ◽  
Olga Ferlian ◽  
Romy Zeiss ◽  
Bernhard Klarner ◽  
...  
Keyword(s):  
Species Richness ◽  
Structural Equation ◽  
Structural Equation Models ◽  
Trophic Levels ◽  
Arthropod Community ◽  
Arthropod Communities ◽  
Earthworm Invasion ◽  
Invasive Earthworms ◽  
Invasion Impacts ◽  
Arthropod Abundance

AbstractDeclining arthropod communities have recently gained a lot of attention with climate and land-use change among the most-frequently discussed drivers. Here, we focus on a seemingly underrepresented driver of arthropod-community decline: biological invasions. For ∼12,000 years, earthworms have been absent from wide parts of northern North America, but they have been re-introduced with dramatic consequences. Most studies investigating earthworm-invasion impacts focus on the belowground world, resulting in limited knowledge on aboveground-community changes. We present observational data on earthworm, plant, and aboveground-arthropod communities in 60 plots, distributed across areas with increasing invasion status (low, medium, high) in a Canadian forest. We analyzed how earthworm-invasion status and biomass impact aboveground arthropod community abundance, biomass, and species richness, and how earthworm impacts cascade across trophic levels. We sampled ∼13,000 arthropods, dominated by Hemiptera, Diptera, Araneae, Thysanoptera, and Hymenoptera. Total arthropod abundance, biomass, and species richness declined significantly from areas of low to those with high invasion status with reductions of 61, 27, and 18%, respectively. Structural Equation Models unraveled that earthworms directly and indirectly impact arthropods across trophic levels. We show that earthworm invasion can alter aboveground multitrophic arthropod communities and suggest that belowground invasions can be important drivers of aboveground-arthropod decline.

scholarly journals Context-dependency in biodiversity-multifunctionality relationships is driven by nitrogen availability and plant functional composition

2020 ◽  
Author(s):  
Noémie A. Pichon ◽  
Seraina L. Cappelli ◽  
Santiago Soliveres ◽  
Tosca Mannall ◽  
Thu Zar Nwe ◽  
...  
Keyword(s):  
Species Richness ◽  
Plant Species ◽  
Functional Diversity ◽  
Experimental Studies ◽  
Plant Species Richness ◽  
Trophic Levels ◽  
Context Dependency ◽  
Composition Gradient ◽  
Nitrogen Enrichment ◽  
Functional Composition

SummaryThe ability of an ecosystem to deliver multiple functions at high levels (multifunctionality) typically increases with biodiversity but there is substantial variation in the strength and direction of biodiversity effects, suggesting context-dependency. However, the drivers of this context dependency have not been identified and understood in comparative meta-analyses or experimental studies. To determine how different factors modulate the effect of diversity on multifunctionality, we conducted a large grassland experiment with 216 communities, crossing a manipulation of plant species richness (1-20 species) with manipulations of resource availability (nitrogen enrichment), plant functional composition (gradient in mean specific leaf area [SLA] to manipulate abundances of fast vs. slow species), plant functional diversity (variance in SLA) and enemy abundance (fungal pathogen removal). We measured ten functions, above and belowground, related to productivity, nutrient cycling and energy transfer between trophic levels, and calculated multifunctionality. Plant species richness and functional diversity both increased multifunctionality, but their effects were context dependent. Species richness increased multifunctionality, but only when communities were assembled with fast growing (high SLA) species. This was because slow species were more redundant in their functional effects, whereas fast species tended to promote different functions. Functional diversity also increased multifunctionality but this effect was dampened by nitrogen enrichment, however, unfertilised, functionally diverse communities still delivered more functions than low diversity, fertilised communities. Our study suggests that a shift towards exploitative communities will not only alter ecosystem functioning but also the strength of biodiversity-functioning relationships, which highlights the potentially complex effects of global change on multifunctionality.

From cells to globe: approaching the dynamics of DMS(P) in the ocean at multiple scales

2004 ◽  
Vol 61 (5) ◽  
pp. 673-684 ◽  
Author(s):  
Rafel Simó
Keyword(s):  
Multiple Scales ◽  
Cellular Level ◽  
Trophic Levels ◽  
Global Ocean ◽  
Surface Mixed Layer ◽  
Sulfur Transfer ◽  
Ocean Level ◽  
Ecosystem Level ◽  
Major Carrier ◽  
The Individual

Major advances in dimethylated sulfur research are being made by approaching its dynamics at multiple scales. At the molecular to cellular level, single-cell techniques in molecular biology allow us to identify the microbes involved in cycling of dimethylated sulfur. Also, we find that dimethylsulfoxide (DMSO) is as ubiquitous as dimethyl sulfoniopropionate (DMSP) in marine plankton, which supports the recent suggestion that both compounds are involved in coping with oxidative stress. At the community level, there is recent evidence for the role of DMSP as a major carrier in organic sulfur transfer and cycling through trophic levels, from phytoplankton to bacteria and to zooplankton through herbivore protozoans. As a consequence, the food web dynamics drive the oceanic emission of atmospheric sulfur. At the ecosystem level, the diverse and intricate effects of the physicochemical setting (light, wind, nutrients) on the oceanic cycling of dimethylated sulfur are being uncovered. A proposed shortcut to detailed understanding of the individual processes presents the depth of the surface mixed layer as the variable that integrates most of the environmental effects and serves for predicting dimethylsulfide (DMS) concentrations, even at the global ocean level. This opens the door to assessing the strength of the DMS biogeophysical system as a climate regulator.

Towards a balanced presentation and objective interpretation of acoustic and trawl survey data, with specific reference to the eastern Scotian Shelf

2016 ◽  
Vol 73 (12) ◽  
pp. 1914-1921 ◽  
Author(s):  
J. Michael Jech ◽  
Ian H. McQuinn
Keyword(s):  
Atlantic Cod ◽  
Management Strategies ◽  
Pelagic Fish ◽  
Trophic Levels ◽  
Fish Abundance ◽  
Forage Fish ◽  
Specific Reference ◽  
Trawl Survey ◽  
Scotian Shelf ◽  
Eastern Canada

A debate has developed over the ecosystem consequences following the collapse of Atlantic cod throughout the coastal waters of eastern Canada. The explosive increase in pelagic fish abundance in scientific bottom-trawl catches on the eastern Scotian Shelf has been interpreted as being due to either (i) a “pelagic outburst” of forage fish abundance resulting from predator release or conversely (ii) a change in pelagic fish vertical distribution leading to a “suprabenthic habitat occupation” thereby increasing their availability to bottom trawls. These two interpretations have diametrically opposing ecological consequences and suggest different management strategies for these important forage fish species. We argue that an objective evaluation of the available evidence supports the hypothesis that the abundance of forage fish has not increased in response to the demise of cod and other top predators, and the reliance on a single sampling gear with low catchability has biased and will continue to bias the interpretation of demographic trends of pelagic fish populations. We advocate that multiple sampling technologies providing alternative perspectives are needed for the monitoring and management of the various trophic levels if we are to achieve a balanced and objective understanding of marine ecosystems.

scholarly journals How habitat-modifying organisms structure the food web of two coastal ecosystems

2016 ◽  
Vol 283 (1826) ◽  
pp. 20152326 ◽  
Author(s):  
Els M. van der Zee ◽  
Christine Angelini ◽  
Laura L. Govers ◽  
Marjolijn J. A. Christianen ◽  
Andrew H. Altieri ◽  
...  
Keyword(s):  
Species Richness ◽  
Food Web ◽  
Food Webs ◽  
Trophic Interactions ◽  
Trophic Levels ◽  
Interaction Networks ◽  
Habitat Modification ◽  
Seagrass Meadows ◽  
Link Density ◽  
Trophic Role

The diversity and structure of ecosystems has been found to depend both on trophic interactions in food webs and on other species interactions such as habitat modification and mutualism that form non-trophic interaction networks. However, quantification of the dependencies between these two main interaction networks has remained elusive. In this study, we assessed how habitat-modifying organisms affect basic food web properties by conducting in-depth empirical investigations of two ecosystems: North American temperate fringing marshes and West African tropical seagrass meadows. Results reveal that habitat-modifying species, through non-trophic facilitation rather than their trophic role, enhance species richness across multiple trophic levels, increase the number of interactions per species (link density), but decrease the realized fraction of all possible links within the food web (connectance). Compared to the trophic role of the most highly connected species, we found this non-trophic effects to be more important for species richness and of more or similar importance for link density and connectance. Our findings demonstrate that food webs can be fundamentally shaped by interactions outside the trophic network, yet intrinsic to the species participating in it. Better integration of non-trophic interactions in food web analyses may therefore strongly contribute to their explanatory and predictive capacity.

Structure and functioning of the eastern Scotian Shelf ecosystem before and after the collapse of groundfish stocks in the early 1990s

2005 ◽  
Vol 62 (7) ◽  
pp. 1453-1473 ◽  
Author(s):  
Alida Bundy
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Trophic Levels ◽  
Total Biomass ◽  
Scotian Shelf ◽  
Mass Balance Models ◽  
Key Species ◽  
Before And After ◽  
Species Groups ◽  
System Properties

The fishery-induced collapse of the Atlantic cod (Gadus morhua) stock on the eastern Scotian Shelf has altered the species composition of this ecosystem. Ecopath mass-balance models of the ecosystem before and after the collapse were developed to explore how the structure, function, and key species of the ecosystem had changed. For the first time, an analysis of uncertainty was conducted to examine the effects of the uncertainty on model estimates. A comparison of the two Ecopath models indicated that although total productivity and total biomass of the ecosystem remained similar, there were changes in predator structure, trophic structure, and energy flow, many of which were robust to uncertainty. Biomass has significantly increased at trophic levels 3 and 4, and the composition of these trophic levels has changed as a result of the mean increase in trophic level of many species-groups. Piscivory has increased, presumably because of the high abundance of small pelagic fish, and the ratio of pelagic feeders to demersal feeders has increased from 0.3 to 3.0. Thus, the ecosystem has changed from a demersal-feeder-dominated system to a pelagic-feeder-dominated system. Although uncertainty remains concerning some model estimates, the ecosystem has been profoundly altered and exhibits classic symptoms of "fishing down the food web". However, overall system properties were generally conserved.

Pyramids of species richness: the determinants and distribution of species diversity across trophic levels

Oikos ◽  
2016 ◽  
Vol 125 (9) ◽  
pp. 1224-1232 ◽  
Author(s):  
Shaun Turney ◽  
Christopher M. Buddle
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Trophic Levels

The role of Spadefoot Toad tadpoles in wetland trophic structure as influenced by environmental and morphological factors

2011 ◽  
Vol 89 (1) ◽  
pp. 47-59 ◽  
Author(s):  
D. M. Ghioca-Robrecht ◽  
L. M. Smith
Keyword(s):  
Body Size ◽  
Great Plains ◽  
Trophic Structure ◽  
Trophic Levels ◽  
Wetland Ecosystems ◽  
Southern Great Plains ◽  
Larval Amphibians ◽  
Spadefoot Toad ◽  
Spea Bombifrons ◽  
And Function

Larval amphibians reach high densities in playa wetlands in the Southern Great Plains (SGP), USA, and thus may influence the entire structure and function of these ecosystems. We investigated whether both carnivorous and omnivorous morphotypes of Spadefoot Toad tadpoles (New Mexico Spadefoot, Spea multiplicata (Cope, 1863), and Plains Spadefoot, Spea bombifrons (Cope, 1863)) would exhibit a macrophagous feeding behavior that would allow them to occupy several trophic levels in playas. We also compared tadpole diets and foregut widths as influenced by the land use surrounding playas (cultivated versus grassland watersheds), year (dry versus wet year), and body size (snout-to-vent length). Tadpole diets were dominated by detritus and diatoms and tadpole foreguts increased with body size. Generally, more arthropods and less cyanobacteria were found in Spea tadpole diets as tadpoles grew larger, suggesting they influence different trophic levels with age. Foreguts were wider in carnivores than omnivores, suggesting carnivores had increased ability to ingest larger prey. Also, omnivores had wider foreguts in cropland than grassland playas, suggesting they ingest larger food items in cropland playas. From estimates of the amounts of invertebrates, detritus, and algae consumed by Spea tadpoles, we demonstrate that these larvae influence the entire trophic structure of wetland ecosystems.

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