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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) Annual time series of biological variables; integrated primary production rate (PPR), blue line (mmol N m−2 d−1); integrated zooplankton biomass, orange line (mmol N m−2 d−1) and catches per unit effort (CPUE), black line (tons GT−1) during the analyzed period. (b) Scatterplot of PPR versus CPUE (blue dots) and zooplankton biomass versus CPUE (orange dots). Statistics of the linear fittings (blue and orange lines) are inserted.
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fig02: (a) Annual time series of biological variables; integrated primary production rate (PPR), blue line (mmol N m−2 d−1); integrated zooplankton biomass, orange line (mmol N m−2 d−1) and catches per unit effort (CPUE), black line (tons GT−1) during the analyzed period. (b) Scatterplot of PPR versus CPUE (blue dots) and zooplankton biomass versus CPUE (orange dots). Statistics of the linear fittings (blue and orange lines) are inserted.

Mentions: Annual mean values of PPR and zooplankton biomass integrated in the upper 120 m of the water column were computed for the entire 1960–2010 time period (blue and orange lines in Figure 2a). The fisheries CPUE data series covering the same time period is plotted against time in Figure 2a. The temporal evolutions of all variables follow a similar pattern, with low values during the first 15 years (approximately 1960–1975), a substantial increase until approximately 1985 and a later stabilization until 2010. There are statistically positive and significant relationships between biogeochemical variables and the CPUE data (Figure 2b). Correlation coefficients are higher with zooplankton biomass than with PPR (Figure 2b), although in both cases R is above 0.66. For all of the correlation analyses, the probability of significance (p) was adjusted to correct for temporal autocorrelation following the recommendations by Pyper and Peterman [1998]. In all cases, correlations are significant to a 95% confidence level.


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) Annual time series of biological variables; integrated primary production rate (PPR), blue line (mmol N m−2 d−1); integrated zooplankton biomass, orange line (mmol N m−2 d−1) and catches per unit effort (CPUE), black line (tons GT−1) during the analyzed period. (b) Scatterplot of PPR versus CPUE (blue dots) and zooplankton biomass versus CPUE (orange dots). Statistics of the linear fittings (blue and orange lines) are inserted.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig02: (a) Annual time series of biological variables; integrated primary production rate (PPR), blue line (mmol N m−2 d−1); integrated zooplankton biomass, orange line (mmol N m−2 d−1) and catches per unit effort (CPUE), black line (tons GT−1) during the analyzed period. (b) Scatterplot of PPR versus CPUE (blue dots) and zooplankton biomass versus CPUE (orange dots). Statistics of the linear fittings (blue and orange lines) are inserted.
Mentions: Annual mean values of PPR and zooplankton biomass integrated in the upper 120 m of the water column were computed for the entire 1960–2010 time period (blue and orange lines in Figure 2a). The fisheries CPUE data series covering the same time period is plotted against time in Figure 2a. The temporal evolutions of all variables follow a similar pattern, with low values during the first 15 years (approximately 1960–1975), a substantial increase until approximately 1985 and a later stabilization until 2010. There are statistically positive and significant relationships between biogeochemical variables and the CPUE data (Figure 2b). Correlation coefficients are higher with zooplankton biomass than with PPR (Figure 2b), although in both cases R is above 0.66. For all of the correlation analyses, the probability of significance (p) was adjusted to correct for temporal autocorrelation following the recommendations by Pyper and Peterman [1998]. In all cases, correlations are significant to a 95% confidence level.

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