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Biogeochemical control of marine productivity in the Mediterranean Sea during the last 50 years.

Macias D, Garcia-Gorriz E, Piroddi C, Stips A - Global Biogeochem Cycles (2014)

Bottom Line: Almost identical low-frequency signals are found in the nutrient loads of the rivers and in the integrated nutrient levels in the surface marine ecosystem.That result seems to indicate that the control of marine productivity (plankton to fish) in the Mediterranean is principally mediated through bottom-up processes that could be traced back to the characteristics of riverine discharges.Biogeochemical evolution of the Mediterranean over the past 50 yearsRiver nutrient loads drive primary and secondary productionsStrong link between low trophic levels and fisheries.

View Article: PubMed Central - PubMed

Affiliation: European Commission, Joint Research Centre, Institute for Environment and Sustainability, Water Research Unit Ispra, Italy.

ABSTRACT

: The temporal dynamics of biogeochemical variables derived from a coupled 3-D model of the Mediterranean Sea are evaluated for the last 50 years (1960-2010) against independent data on fisheries catch per unit effort (CPUE) for the same time period. Concordant patterns are found in the time series of all of the biological variables (from the model and from fisheries statistics), with low values at the beginning of the series, a later increase, with maximum levels reached at the end of the 1990s, and a posterior stabilization. Spectral analysis of the annual biological time series reveals coincident low-frequency signals in all of them. The first, more energetic signal peaks around the year 2000, while the second, less energetic signal peaks near 1982. Almost identical low-frequency signals are found in the nutrient loads of the rivers and in the integrated nutrient levels in the surface marine ecosystem. Nitrate concentration shows a maximum level in 1998, with a later stabilization to present-day values, coincident with the first low-frequency signal found in the biological series. Phosphate shows maximum concentrations around 1982 and a posterior sharp decline, in concordance with the second low-frequency signal observed in the biological series. That result seems to indicate that the control of marine productivity (plankton to fish) in the Mediterranean is principally mediated through bottom-up processes that could be traced back to the characteristics of riverine discharges. The high sensitivity of CPUE time series to environmental conditions might be another indicator of the overexploitation of this marine ecosystem.

Key points: Biogeochemical evolution of the Mediterranean over the past 50 yearsRiver nutrient loads drive primary and secondary productionsStrong link between low trophic levels and fisheries.

No MeSH data available.


Related in: MedlinePlus

(a) Main signals found in the biological time series using SSA. (b) Secondary signals found in the biological time series using SSA. (c) Scatterplot of the main signals found in PPR versus the main signals found in the CPUE time series. Statistics of the linear fit is inserted. (d) Scatterplot of the main signals found in zooplankton biomass versus the main signals found in the CPUE time series. Statistics of the linear fit is inserted.
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fig03: (a) Main signals found in the biological time series using SSA. (b) Secondary signals found in the biological time series using SSA. (c) Scatterplot of the main signals found in PPR versus the main signals found in the CPUE time series. Statistics of the linear fit is inserted. (d) Scatterplot of the main signals found in zooplankton biomass versus the main signals found in the CPUE time series. Statistics of the linear fit is inserted.

Mentions: Two main signals were identified as the main contributors to the total variability of the time series and explained between 69% and 90% of their total variability (Table 1). The identified signals had specific and concordant shapes (Figures 3a and 3b). Signal 1, which explains approximately 50% of the total variability of the individual series (Table 1), has a sigmoidal shape (Figure 3a) with minimum values near 1965 and maximum values near 1998. Signal 2 accounts for 25–30% of the total variability (Table 1) and has a distinctive peak during the second half of the 1980s (Figure 3b), with lower values before and after. The scatterplots of the signals in the biogeochemical variables time series against the signals in the CPUE data (Figures 3c and 3d) show very high (r2 > 0.95), significant (p < 0.001) relationships, indicating that the isolated signals could be representing common processes driving the main dynamics of the different time series.


Biogeochemical control of marine productivity in the Mediterranean Sea during the last 50 years.

Macias D, Garcia-Gorriz E, Piroddi C, Stips A - Global Biogeochem Cycles (2014)

(a) Main signals found in the biological time series using SSA. (b) Secondary signals found in the biological time series using SSA. (c) Scatterplot of the main signals found in PPR versus the main signals found in the CPUE time series. Statistics of the linear fit is inserted. (d) Scatterplot of the main signals found in zooplankton biomass versus the main signals found in the CPUE time series. Statistics of the linear fit is inserted.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493898&req=5

fig03: (a) Main signals found in the biological time series using SSA. (b) Secondary signals found in the biological time series using SSA. (c) Scatterplot of the main signals found in PPR versus the main signals found in the CPUE time series. Statistics of the linear fit is inserted. (d) Scatterplot of the main signals found in zooplankton biomass versus the main signals found in the CPUE time series. Statistics of the linear fit is inserted.
Mentions: Two main signals were identified as the main contributors to the total variability of the time series and explained between 69% and 90% of their total variability (Table 1). The identified signals had specific and concordant shapes (Figures 3a and 3b). Signal 1, which explains approximately 50% of the total variability of the individual series (Table 1), has a sigmoidal shape (Figure 3a) with minimum values near 1965 and maximum values near 1998. Signal 2 accounts for 25–30% of the total variability (Table 1) and has a distinctive peak during the second half of the 1980s (Figure 3b), with lower values before and after. The scatterplots of the signals in the biogeochemical variables time series against the signals in the CPUE data (Figures 3c and 3d) show very high (r2 > 0.95), significant (p < 0.001) relationships, indicating that the isolated signals could be representing common processes driving the main dynamics of the different time series.

Bottom Line: Almost identical low-frequency signals are found in the nutrient loads of the rivers and in the integrated nutrient levels in the surface marine ecosystem.That result seems to indicate that the control of marine productivity (plankton to fish) in the Mediterranean is principally mediated through bottom-up processes that could be traced back to the characteristics of riverine discharges.Biogeochemical evolution of the Mediterranean over the past 50 yearsRiver nutrient loads drive primary and secondary productionsStrong link between low trophic levels and fisheries.

View Article: PubMed Central - PubMed

Affiliation: European Commission, Joint Research Centre, Institute for Environment and Sustainability, Water Research Unit Ispra, Italy.

ABSTRACT

: The temporal dynamics of biogeochemical variables derived from a coupled 3-D model of the Mediterranean Sea are evaluated for the last 50 years (1960-2010) against independent data on fisheries catch per unit effort (CPUE) for the same time period. Concordant patterns are found in the time series of all of the biological variables (from the model and from fisheries statistics), with low values at the beginning of the series, a later increase, with maximum levels reached at the end of the 1990s, and a posterior stabilization. Spectral analysis of the annual biological time series reveals coincident low-frequency signals in all of them. The first, more energetic signal peaks around the year 2000, while the second, less energetic signal peaks near 1982. Almost identical low-frequency signals are found in the nutrient loads of the rivers and in the integrated nutrient levels in the surface marine ecosystem. Nitrate concentration shows a maximum level in 1998, with a later stabilization to present-day values, coincident with the first low-frequency signal found in the biological series. Phosphate shows maximum concentrations around 1982 and a posterior sharp decline, in concordance with the second low-frequency signal observed in the biological series. That result seems to indicate that the control of marine productivity (plankton to fish) in the Mediterranean is principally mediated through bottom-up processes that could be traced back to the characteristics of riverine discharges. The high sensitivity of CPUE time series to environmental conditions might be another indicator of the overexploitation of this marine ecosystem.

Key points: Biogeochemical evolution of the Mediterranean over the past 50 yearsRiver nutrient loads drive primary and secondary productionsStrong link between low trophic levels and fisheries.

No MeSH data available.


Related in: MedlinePlus