Atmospheric phosphorus deposition may cause lakes to revert from phosphorus limitation back to nitrogen limitation

Abstract

Recent findings indicate that increased atmospheric deposition of nitrogen of human origin has caused changes in the pattern of ecological nutrient limitation in lakes in the northern hemisphere. An increase in the nitrogen to phosphorus ratio, and hence a shift from pristine nitrogen limitation to human-induced phosphorus limitation of phytoplankton growth, seems to have been driven by deposition of atmospheric nitrogen. These findings challenge the classical paradigm of lake phytoplankton productivity being naturally limited by phosphorus availability. However, atmospheric phosphorus deposition may also be highly relevant. Here we show how dissolved inorganic nitrogen concentration has decreased in the Pyrenean lake district over recent decades, despite there being an increase in deposition of atmospheric nitrogen. This is related to an increased atmospheric phosphorus load in the lake water, as a result of higher atmospheric inputs. These changes are causing phytoplankton to revert from being phosphorus-limited to being nitrogen-limited.

Atmospheric Chemical Loadings in the High Mountain: Current Forcing and Legacy Pollution

“…14.5). In an opposite way, the concentration of dissolved inorganic nitrogen has decreased with time in the lakes (Camarero and Catalan 2012).…”

“…Phosphorus comes largely from South, accompanying the dust outbreaks reaching the Pyrenees from Northern Africa and the Iberian Peninsula (Camarero and Catalan 2012). There is a certain correlation between the North Atlantic Oscillation (NAO) index and the production of dust in Northern Africa and subsequent transport towards the Mediterranean (Moulin et al 1997).…”

“…A higher frequency of positive NAO values in the mid part of the period likely correlates with more frequent dust outbreak episodes carrying phosphorus from Northern Africa to the Pyrenees. This would indicate a certain meteorological control on the transport of atmospheric phosphorus (after Camarero and Catalan 2012) either part of a longer trend or a mere fluctuation. But in any case, what can be deduced from it is that the anthropogenic nitrogen inputs, by causing phosphorus limitation, have made the lake more sensitive to any natural or human-induced phosphorus input than it would be otherwise.…”

“…However, there is a difference. The inputs of both (Camarero and Catalan 2012). Right trend-line showing the evolution of NO x emissions in Spain (Source EMEP, http://www.ceip.at/ms/ceip_home1/ceip_home/webdab_ emepdatabase/emissions_emepmodels/) The overimposed dots represent yearly DIN deposition as measured at the Lake Redon station.…”

Consequence of altered nitrogen cycles in the coupled human and ecological system under changing climate: The need for long-term and site-based research

“…Bergström and Jansson (2006) have shown that increased N deposition may have changed lakes from N-limitation to P-limitation in remote and small lakes across the northern hemisphere, an observation supported by nutrient addition experiments in UK upland streams (Maberly et al 2002). On the other hand, an assessment of long-term data from a Spanish ILTER lake site by Camarero and Catalan (2012) suggested that atmospheric P deposition may cause lakes to revert from P-limitation to N-limitation. There are clear needs for research into longterm C-N-P interactions for a much wider range of biomes.…”