Spatial trends and environmental drivers of epibenthic shelf community structure across the Aleutian Islands

Bland, Aaron; Konar, Brenda; Edwards, Matthew S.

doi:10.1016/j.csr.2019.01.006

Cited by 6 publications

(5 citation statements)

References 92 publications

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“…During two cruises aboard the R/V Oceanus in 2016 and 2017, we deployed cBITs in each of the three habitats (kelp forest, urchin barrens, transition habitats) on each of nine islands (Table 1; Figs 1,2 and 8) for 36-hour periods to measure both day and night patterns of NEP and Re, and to ensure we captured a complete diurnal cycle. These islands span more than 1000 km and therefore experience differences in temperature, salinity, wave exposure and other biotic factors [62]. Consequently, all cBITs deployments were done in the summer (i.e.…”

Section: Experimental Designmentioning

confidence: 99%

Marine deforestation leads to widespread loss of ecosystem function

et al. 2020

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Trophic interactions can result in changes to the abundance and distribution of habitat-forming species that dramatically reduce ecosystem functioning. In the coastal zone of the Aleutian Archipelago, overgrazing by herbivorous sea urchins that began in the 1990s resulted in widespread deforestation of the region's kelp forests, which led to lower macroalgal abundances and higher benthic irradiances. We examined how this deforestation impacted ecosystem function by comparing patterns of net ecosystem production (NEP), gross primary production (GPP), ecosystem respiration (Re), and the range between GPP and Re in remnant kelp forests, urchin barrens, and habitats that were in transition between the two habitat types at nine islands that spanned more than 1000 kilometers of the archipelago. Our results show that deforestation, on average, resulted in a 24% reduction in GPP, a 26% reduction in Re, and a 24% reduction in the range between GPP and Re. Further, the transition habitats were intermediate to the kelp forests and urchin barrens for these metrics. These opposing metabolic processes remained in balance; however, which resulted in little-to-no changes to NEP. These effects of deforestation on ecosystem productivity, however, were highly variable between years and among the study islands. In light of the worldwide declines in kelp forests observed in recent decades, our findings suggest that marine deforestation profoundly affects how coastal ecosystems function.of the region's river systems and its riparian plant communities [4,5]. Similarly, large marine algae, such as kelps, can form subtidal forests whose biogenic structures alter hydrodynamic, nutrient and light conditions, modify patterns of biodiversity, enhance primary production and carbon sequestration, and provide food and habitat for numerous other species [6][7][8][9]. Consequently, the loss of these forest-forming kelps and the benthic communities they support can have dramatic impacts to how nearshore ecosystems function, especially if they occur over large geographic areas. Indeed, kelp deforestation has occurred in numerous areas worldwide in recent decades due to a variety of forcing factors [10,11], and the subtidal rocky reefs of the Aleutian Archipelago serve as a model system to investigate the broader impacts of such deforestation. These forests have historically been dominated by dense populations of the surface canopy-forming kelp Eualaria fistulosa, several species of understory kelps such as Laminaria spp. and Agarum spp., the brown alga Desmarestia spp., and numerous species of fleshy read algae. However, the collapse of sea otter (Enhydra lutris) populations led to large increases in their primary prey, herbivorous sea urchins (Strongylocentrotus polyacanthus), which subsequently resulted in overgrazing and widespread losses of the region's kelp forests [12]. This collapse began in the late 1990s, likely in response to a dietary shift by killer whales toward sea otters, and by 2000 sea otter densities had declined throughout the ar...

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Section: Experimental Designmentioning

confidence: 99%

Marine deforestation leads to widespread loss of ecosystem function

et al. 2020

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“…Large kelps such as A. clathratum additionally require a stable foundation for holdfast attachment to endure currents and storm surge (Morrison et al, 2009;Watanabe et al, 2014;Masteller et al, 2015). In contrast, E. parma would preferentially inhabit coarse sand areas (Stanley and James, 1971;Sisson et al, 2002), enabling filtering where coarse sand traps particulate matter for consumption without excess fouling (Bland et al, 2019), and burying to avoid predation (Manderson et al, 1999;Pappal et al, 2012) and damaging storm surge (O'Neill, 1978). Distance from the coast may act as a surrogate for sedimentation rate (Stephens and Diesing, 2015;Misiuk et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Spatial distribution of benthic flora and fauna of coastal placentia bay, an ecologically and biologically significant area of the island of newfoundland, atlantic Canada

Mackin-McLaughlin

Nemani²,

Misiuk³

et al. 2022

Front. Environ. Sci.

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Coastal habitats have the potential to be biodiversity hotspots that provide important ecosystem services, but also hotspots for human development and exploitation. Continued use of coastal ecosystem services requires establishing baselines that capture the present state of the benthos. This study employs habitat mapping to establish a baseline describing the spatial distribution of benthic organisms along the western coast of Placentia Bay, an Ecologically and Biologically Significant Area (EBSA) in Newfoundland, Canada. The influence of seafloor characteristics on the distribution of four dominant epifaunal assemblages and two macrophyte species were modelled using two machine learning techniques: the well-established Random Forest and the newer Light Gradient Boosting Machine. When investigating model performance, the inclusion of fine-scale (<1 m) substrate information from the benthic videos was found to consistently improve model accuracy. Predictive maps developed here suggest that the majority of the surveyed areas consisted of a species-rich epifaunal assemblage dominated by ophiuroids, porifera, and hydrozoans, as well as prominent coverage by Agarum clathratum and non-geniculate crustose coralline algae. These maps establish a baseline that enables future monitoring of Placentia Bay’s coastal ecosystem, helping to conserve the biodiversity and ecosystem services this area provides.

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“…For example, variation in biological interactions can drive variation at small scale (< 10 m) patterns, while habitat heterogeneity can drive local scale (< 10 km) differences in community structure 33,76,77 . At mesoscales (10-100 km) or regional scales (> 100 s km), coastal marine communities may differ across oceanographic boundaries where multiple physical parameters change simultaneously 35,78,79 . This can have important consequences to our understanding of the relative importance of the factors that structure these communities, as small-scale biological interactions can mask the influence of large-scale oceanographic and climate factors [51][52][53] , while large-scale factors can mask the influence of small-scale biological interactions 33,[62][63][64] .…”

Section: Discussionmentioning

confidence: 99%

Trophic downgrading reduces spatial variability on rocky reefs

Edwards

Konar

2020

Sci Rep

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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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Spatial trends and environmental drivers of epibenthic shelf community structure across the Aleutian Islands

Cited by 6 publications

References 92 publications

Marine deforestation leads to widespread loss of ecosystem function

Marine deforestation leads to widespread loss of ecosystem function

Spatial distribution of benthic flora and fauna of coastal placentia bay, an ecologically and biologically significant area of the island of newfoundland, atlantic Canada

Trophic downgrading reduces spatial variability on rocky reefs

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