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Towards an Understanding of the Interactions between Freshwater Inflows and Phytoplankton Communities in a Subtropical Estuary in the Gulf of Mexico.

Dorado S, Booe T, Steichen J, McInnes AS, Windham R, Shepard A, Lucchese AE, Preischel H, Pinckney JL, Davis SE, Roelke DL, Quigg A - PLoS ONE (2015)

Bottom Line: Subtropical estuaries worldwide face increased pressure on their ecosystem health and services due to increasing human population growth and associated land use/land cover changes, expansion of ports, and climate change.Temporally, temperature and variables associated with freshwater inflow (discharge volume, salinity, inorganic nitrogen and phosphorus concentrations) were major influences on phytoplankton dynamics.Given the differential influences of freshwater inflow on the phytoplankton communities of Galveston Bay, alterations upstream (magnitude, timing, frequency) will likely have a profound effect on downstream ecological processes and corresponding ecosystem services.

View Article: PubMed Central - PubMed

Affiliation: Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas, 77553, United States of America.

ABSTRACT
Subtropical estuaries worldwide face increased pressure on their ecosystem health and services due to increasing human population growth and associated land use/land cover changes, expansion of ports, and climate change. We investigated freshwater inflows (river discharge) and the physico-chemical characteristics of Galveston Bay (Texas, USA) as mechanisms driving variability in phytoplankton biomass and community composition between February 2008 and December 2009. Results of multivariate analyses (hierarchical cluster analysis, PERMANOVA, Mantel test, and nMDS ordination coupled to environmental vector fitting) revealed that temporal and spatial differences in phytoplankton community structure correlate to differences in hydrographic and water quality parameters. Spatially, phytoplankton biomass and community composition responded to nutrient loading from the San Jacinto River in the northwest region of the bay (consistent with nutrient limitation) while hydraulic displacement (and perhaps other processes) resulted in overall lower biomass in the Trinity River delta (northeast region). The influence of inflows on phytoplankton diminished along a north to south gradient in the bay. Temporally, temperature and variables associated with freshwater inflow (discharge volume, salinity, inorganic nitrogen and phosphorus concentrations) were major influences on phytoplankton dynamics. Dissolved inorganic nitrogen: phosphorus (DIN:DIP) ratios suggest that phytoplankton communities will be predominately nitrogen limited. Diatoms dominated during periods of moderate to high freshwater inflows in winter/spring and were more abundant in the upper bay while cyanobacteria dominated during summer/fall when inflow was low. Given the differential influences of freshwater inflow on the phytoplankton communities of Galveston Bay, alterations upstream (magnitude, timing, frequency) will likely have a profound effect on downstream ecological processes and corresponding ecosystem services.

No MeSH data available.


Spearman’s correlation among environmental distances and (A) pigment concentration and (B) relative pigment abundance dissimilarity matrices.Environmental distances represent Euclidean distance, and pigment dissimilarity was calculated using the Bray-Curtis index. Correlation and significance of correlation among matrices was assessed using the Mantel test.
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pone.0130931.g005: Spearman’s correlation among environmental distances and (A) pigment concentration and (B) relative pigment abundance dissimilarity matrices.Environmental distances represent Euclidean distance, and pigment dissimilarity was calculated using the Bray-Curtis index. Correlation and significance of correlation among matrices was assessed using the Mantel test.

Mentions: To further investigate the relationship between the environmental variables and phytoplankton in Galveston Bay, we used the Mantel test to directly correlate their respective dissimilarity matrices. Individual pigment concentration and relative pigment abundances were significantly correlated (Spearman’s ρ values = 0.36 and 0.29, respectively; p < 0.001) to environmental distances representing the overall environmental conditions (i.e., the combination of all 16 individual parameters) (Fig 5A and 5B respectively). This suggests that differences in the phytoplankton community structure increased along changing environmental gradients. To pinpoint the environmental properties that had the greatest influence on phytoplankton communities, we assessed the correlation of single environmental variable distances to the phytoplankton dissimilarities (Table 3). Our results show the dissimilarity in pigment concentrations was significantly (p < 0.05) related to differences in temperature (ρ = 0.28), Fv/Fm (ρ = 0.18), NOx (ρ = 0.18), NH4+ (ρ = 0.18), TP (ρ = 0.07), overall biomass (chl a, ρ = 0.71), DIN (ρ = 0.20), average freshwater discharge (ρ = 0.11) and maximum freshwater discharge (ρ = 0.11). When the relative abundance of pigments was tested, significant correlations (p < 0.05) included temperature (ρ = 0.30), salinity (ρ = 0.08), Fv/Fm (ρ = 0.14), NOx (ρ = 0.11), NH4+ (ρ = 0.10), Pi (ρ = 0.05), TP (ρ = 0.11), overall biomass (ρ = 0.15), DIN (ρ = 0.10), average freshwater discharge (ρ = 0.23) and maximum freshwater discharge (ρ = 0.24). Properties of freshwater inflow were found to correlate to differences in phytoplankton biomass and community composition which supports hierarchical cluster analysis and PERMANOVA results (Table 3).


Towards an Understanding of the Interactions between Freshwater Inflows and Phytoplankton Communities in a Subtropical Estuary in the Gulf of Mexico.

Dorado S, Booe T, Steichen J, McInnes AS, Windham R, Shepard A, Lucchese AE, Preischel H, Pinckney JL, Davis SE, Roelke DL, Quigg A - PLoS ONE (2015)

Spearman’s correlation among environmental distances and (A) pigment concentration and (B) relative pigment abundance dissimilarity matrices.Environmental distances represent Euclidean distance, and pigment dissimilarity was calculated using the Bray-Curtis index. Correlation and significance of correlation among matrices was assessed using the Mantel test.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4489867&req=5

pone.0130931.g005: Spearman’s correlation among environmental distances and (A) pigment concentration and (B) relative pigment abundance dissimilarity matrices.Environmental distances represent Euclidean distance, and pigment dissimilarity was calculated using the Bray-Curtis index. Correlation and significance of correlation among matrices was assessed using the Mantel test.
Mentions: To further investigate the relationship between the environmental variables and phytoplankton in Galveston Bay, we used the Mantel test to directly correlate their respective dissimilarity matrices. Individual pigment concentration and relative pigment abundances were significantly correlated (Spearman’s ρ values = 0.36 and 0.29, respectively; p < 0.001) to environmental distances representing the overall environmental conditions (i.e., the combination of all 16 individual parameters) (Fig 5A and 5B respectively). This suggests that differences in the phytoplankton community structure increased along changing environmental gradients. To pinpoint the environmental properties that had the greatest influence on phytoplankton communities, we assessed the correlation of single environmental variable distances to the phytoplankton dissimilarities (Table 3). Our results show the dissimilarity in pigment concentrations was significantly (p < 0.05) related to differences in temperature (ρ = 0.28), Fv/Fm (ρ = 0.18), NOx (ρ = 0.18), NH4+ (ρ = 0.18), TP (ρ = 0.07), overall biomass (chl a, ρ = 0.71), DIN (ρ = 0.20), average freshwater discharge (ρ = 0.11) and maximum freshwater discharge (ρ = 0.11). When the relative abundance of pigments was tested, significant correlations (p < 0.05) included temperature (ρ = 0.30), salinity (ρ = 0.08), Fv/Fm (ρ = 0.14), NOx (ρ = 0.11), NH4+ (ρ = 0.10), Pi (ρ = 0.05), TP (ρ = 0.11), overall biomass (ρ = 0.15), DIN (ρ = 0.10), average freshwater discharge (ρ = 0.23) and maximum freshwater discharge (ρ = 0.24). Properties of freshwater inflow were found to correlate to differences in phytoplankton biomass and community composition which supports hierarchical cluster analysis and PERMANOVA results (Table 3).

Bottom Line: Subtropical estuaries worldwide face increased pressure on their ecosystem health and services due to increasing human population growth and associated land use/land cover changes, expansion of ports, and climate change.Temporally, temperature and variables associated with freshwater inflow (discharge volume, salinity, inorganic nitrogen and phosphorus concentrations) were major influences on phytoplankton dynamics.Given the differential influences of freshwater inflow on the phytoplankton communities of Galveston Bay, alterations upstream (magnitude, timing, frequency) will likely have a profound effect on downstream ecological processes and corresponding ecosystem services.

View Article: PubMed Central - PubMed

Affiliation: Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas, 77553, United States of America.

ABSTRACT
Subtropical estuaries worldwide face increased pressure on their ecosystem health and services due to increasing human population growth and associated land use/land cover changes, expansion of ports, and climate change. We investigated freshwater inflows (river discharge) and the physico-chemical characteristics of Galveston Bay (Texas, USA) as mechanisms driving variability in phytoplankton biomass and community composition between February 2008 and December 2009. Results of multivariate analyses (hierarchical cluster analysis, PERMANOVA, Mantel test, and nMDS ordination coupled to environmental vector fitting) revealed that temporal and spatial differences in phytoplankton community structure correlate to differences in hydrographic and water quality parameters. Spatially, phytoplankton biomass and community composition responded to nutrient loading from the San Jacinto River in the northwest region of the bay (consistent with nutrient limitation) while hydraulic displacement (and perhaps other processes) resulted in overall lower biomass in the Trinity River delta (northeast region). The influence of inflows on phytoplankton diminished along a north to south gradient in the bay. Temporally, temperature and variables associated with freshwater inflow (discharge volume, salinity, inorganic nitrogen and phosphorus concentrations) were major influences on phytoplankton dynamics. Dissolved inorganic nitrogen: phosphorus (DIN:DIP) ratios suggest that phytoplankton communities will be predominately nitrogen limited. Diatoms dominated during periods of moderate to high freshwater inflows in winter/spring and were more abundant in the upper bay while cyanobacteria dominated during summer/fall when inflow was low. Given the differential influences of freshwater inflow on the phytoplankton communities of Galveston Bay, alterations upstream (magnitude, timing, frequency) will likely have a profound effect on downstream ecological processes and corresponding ecosystem services.

No MeSH data available.