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Pelagic Sargassum community change over a 40-year period: temporal and spatial variability.

Huffard CL, von Thun S, Sherman AD, Sealey K, Smith KL - Mar. Biol. (2014)

Bottom Line: Recent community structures were unlike any documented historically, whether compared to sites of the same latitude range within the Sargasso Sea, or the broader historical dataset of sites ranging across the Sargasso Sea, Gulf Stream, and south of the subtropical convergence zone.The diversity and species composition of macrofauna communities associated with Sargassum might be inherently unstable.While several biological and oceanographic factors might have contributed to these observations, including a decline in pH, increase in summer temperatures, and changes in the abundance and distribution of Sargassum seaweed in the area, it is not currently possible to attribute direct causal links.

View Article: PubMed Central - PubMed

Affiliation: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039 USA.

ABSTRACT
Pelagic forms of the brown algae (Phaeophyceae) Sargassum spp. and their conspicuous rafts are defining characteristics of the Sargasso Sea in the western North Atlantic. Given rising temperatures and acidity in the surface ocean, we hypothesized that macrofauna associated with Sargassum in the Sargasso Sea have changed with respect to species composition, diversity, evenness, and sessile epibiota coverage since studies were conducted 40 years ago. Sargassum communities were sampled along a transect through the Sargasso Sea in 2011 and 2012 and compared to samples collected in the Sargasso Sea, Gulf Stream, and south of the subtropical convergence zone from 1966 to 1975. Mobile macrofauna communities exhibited changes in community structure and declines in diversity and evenness within a 6-month time period (August 2011-February 2012). Equivalent declines in diversity and evenness were recorded in the same region (Sargasso Sea, 25°-29°N) in 1972-1973. Recent community structures were unlike any documented historically, whether compared to sites of the same latitude range within the Sargasso Sea, or the broader historical dataset of sites ranging across the Sargasso Sea, Gulf Stream, and south of the subtropical convergence zone. Recent samples also recorded low coverage by sessile epibionts, both calcifying forms and hydroids. The diversity and species composition of macrofauna communities associated with Sargassum might be inherently unstable. While several biological and oceanographic factors might have contributed to these observations, including a decline in pH, increase in summer temperatures, and changes in the abundance and distribution of Sargassum seaweed in the area, it is not currently possible to attribute direct causal links.

No MeSH data available.


Related in: MedlinePlus

Trophic groups of mobile macrofauna associated with Sargassum in recent and historical samples. Relative fraction of all individuals in each sample represented by each trophic group, an average of all samples in each latitude block ± standard deviation error bars. Groups specified by an R represent recent surveys. The other/unknown category includes parasites and taxa for which diets were unknown. Trophic category designations and citations in Online Resource 3
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Fig6: Trophic groups of mobile macrofauna associated with Sargassum in recent and historical samples. Relative fraction of all individuals in each sample represented by each trophic group, an average of all samples in each latitude block ± standard deviation error bars. Groups specified by an R represent recent surveys. The other/unknown category includes parasites and taxa for which diets were unknown. Trophic category designations and citations in Online Resource 3

Mentions: Recent samples were dominated by mobile macrofauna that are predators of other mobile macrofauna (Fig. 6; Online Resource 3), a pattern dominated by relatively high abundance of the decapod crustacean Latreutes fucorum compared to the other organisms of known trophic group. By contrast, historical sites to the south had a higher relative representation of epibiont predators and detritivores, and historical sites to the north had a higher relative representation of herbivores and detritivores. We were unable to define the diet of Litiopa melanostoma, a gastropod that was common in historical datasets.Fig. 6


Pelagic Sargassum community change over a 40-year period: temporal and spatial variability.

Huffard CL, von Thun S, Sherman AD, Sealey K, Smith KL - Mar. Biol. (2014)

Trophic groups of mobile macrofauna associated with Sargassum in recent and historical samples. Relative fraction of all individuals in each sample represented by each trophic group, an average of all samples in each latitude block ± standard deviation error bars. Groups specified by an R represent recent surveys. The other/unknown category includes parasites and taxa for which diets were unknown. Trophic category designations and citations in Online Resource 3
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4231207&req=5

Fig6: Trophic groups of mobile macrofauna associated with Sargassum in recent and historical samples. Relative fraction of all individuals in each sample represented by each trophic group, an average of all samples in each latitude block ± standard deviation error bars. Groups specified by an R represent recent surveys. The other/unknown category includes parasites and taxa for which diets were unknown. Trophic category designations and citations in Online Resource 3
Mentions: Recent samples were dominated by mobile macrofauna that are predators of other mobile macrofauna (Fig. 6; Online Resource 3), a pattern dominated by relatively high abundance of the decapod crustacean Latreutes fucorum compared to the other organisms of known trophic group. By contrast, historical sites to the south had a higher relative representation of epibiont predators and detritivores, and historical sites to the north had a higher relative representation of herbivores and detritivores. We were unable to define the diet of Litiopa melanostoma, a gastropod that was common in historical datasets.Fig. 6

Bottom Line: Recent community structures were unlike any documented historically, whether compared to sites of the same latitude range within the Sargasso Sea, or the broader historical dataset of sites ranging across the Sargasso Sea, Gulf Stream, and south of the subtropical convergence zone.The diversity and species composition of macrofauna communities associated with Sargassum might be inherently unstable.While several biological and oceanographic factors might have contributed to these observations, including a decline in pH, increase in summer temperatures, and changes in the abundance and distribution of Sargassum seaweed in the area, it is not currently possible to attribute direct causal links.

View Article: PubMed Central - PubMed

Affiliation: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd, Moss Landing, CA 95039 USA.

ABSTRACT
Pelagic forms of the brown algae (Phaeophyceae) Sargassum spp. and their conspicuous rafts are defining characteristics of the Sargasso Sea in the western North Atlantic. Given rising temperatures and acidity in the surface ocean, we hypothesized that macrofauna associated with Sargassum in the Sargasso Sea have changed with respect to species composition, diversity, evenness, and sessile epibiota coverage since studies were conducted 40 years ago. Sargassum communities were sampled along a transect through the Sargasso Sea in 2011 and 2012 and compared to samples collected in the Sargasso Sea, Gulf Stream, and south of the subtropical convergence zone from 1966 to 1975. Mobile macrofauna communities exhibited changes in community structure and declines in diversity and evenness within a 6-month time period (August 2011-February 2012). Equivalent declines in diversity and evenness were recorded in the same region (Sargasso Sea, 25°-29°N) in 1972-1973. Recent community structures were unlike any documented historically, whether compared to sites of the same latitude range within the Sargasso Sea, or the broader historical dataset of sites ranging across the Sargasso Sea, Gulf Stream, and south of the subtropical convergence zone. Recent samples also recorded low coverage by sessile epibionts, both calcifying forms and hydroids. The diversity and species composition of macrofauna communities associated with Sargassum might be inherently unstable. While several biological and oceanographic factors might have contributed to these observations, including a decline in pH, increase in summer temperatures, and changes in the abundance and distribution of Sargassum seaweed in the area, it is not currently possible to attribute direct causal links.

No MeSH data available.


Related in: MedlinePlus