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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

Multi-dimensional scaling plots of Sargassum-associated mobile macrofauna community structures documented in August 2011 and February 2012 (open shapes, legends designated with an “R”) compared with communities documented in historical samples collected between 1966 and 1975 (Weis 1968; Fine 1970; Butler et al. 1983), all geographic and latitude groups (both orange andwhite triangles in Fig. 1), labeled by a geographic group, b latitude group, c season, and d year
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Fig5: Multi-dimensional scaling plots of Sargassum-associated mobile macrofauna community structures documented in August 2011 and February 2012 (open shapes, legends designated with an “R”) compared with communities documented in historical samples collected between 1966 and 1975 (Weis 1968; Fine 1970; Butler et al. 1983), all geographic and latitude groups (both orange andwhite triangles in Fig. 1), labeled by a geographic group, b latitude group, c season, and d year

Mentions: Recently sampled MMCS were also unlike any sample from the broader historical dataset, including those from samples from as far south as the Caribbean (orange and white triangles in Fig. 1; ANOSIM Global R = 0.606, P = 0.001 %). Recent MMCS were <19 % similar to any single historical sample MMCS (SIMPROF Pi = 6.9, P = 0.1 %), and <15 % similar to any historical sample in the Sargasso Sea (SIMPROF Pi = 5.69, P = 0.1 %; Fig. 5). The MMCS at historical stations in southern latitudes and those from recent stations were significantly different and did not indicate a northward latitudinal shift of species assemblages. Seasonal cyclicity in MMCS was once evident at Sta. S based on historical samples from 1972 and 1973, and in both those years communities returned to approximately the starting community compositions by the end of the year (Online Resource 2 panel a; RELATE test for cyclicity ρ = 0.23, P = 0.01 %). Our recent sample from Station 1 near Hydrostation S was far outside the range of historical variability at Hydrostation S (Online Resource 2 panel b).Fig. 5


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)

Multi-dimensional scaling plots of Sargassum-associated mobile macrofauna community structures documented in August 2011 and February 2012 (open shapes, legends designated with an “R”) compared with communities documented in historical samples collected between 1966 and 1975 (Weis 1968; Fine 1970; Butler et al. 1983), all geographic and latitude groups (both orange andwhite triangles in Fig. 1), labeled by a geographic group, b latitude group, c season, and d year
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4231207&req=5

Fig5: Multi-dimensional scaling plots of Sargassum-associated mobile macrofauna community structures documented in August 2011 and February 2012 (open shapes, legends designated with an “R”) compared with communities documented in historical samples collected between 1966 and 1975 (Weis 1968; Fine 1970; Butler et al. 1983), all geographic and latitude groups (both orange andwhite triangles in Fig. 1), labeled by a geographic group, b latitude group, c season, and d year
Mentions: Recently sampled MMCS were also unlike any sample from the broader historical dataset, including those from samples from as far south as the Caribbean (orange and white triangles in Fig. 1; ANOSIM Global R = 0.606, P = 0.001 %). Recent MMCS were <19 % similar to any single historical sample MMCS (SIMPROF Pi = 6.9, P = 0.1 %), and <15 % similar to any historical sample in the Sargasso Sea (SIMPROF Pi = 5.69, P = 0.1 %; Fig. 5). The MMCS at historical stations in southern latitudes and those from recent stations were significantly different and did not indicate a northward latitudinal shift of species assemblages. Seasonal cyclicity in MMCS was once evident at Sta. S based on historical samples from 1972 and 1973, and in both those years communities returned to approximately the starting community compositions by the end of the year (Online Resource 2 panel a; RELATE test for cyclicity ρ = 0.23, P = 0.01 %). Our recent sample from Station 1 near Hydrostation S was far outside the range of historical variability at Hydrostation S (Online Resource 2 panel b).Fig. 5

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