Juris Aigars

Hypoxia Is Increasing in the Coastal Zone of the Baltic Sea

Hypoxia is a well-described phenomenon in the offshore waters of the Baltic Sea with both the spatial extent and intensity of hypoxia known to have increased due to anthropogenic eutrophication, however, an unknown amount of hypoxia is present in the coastal zone. Here we report on the widespread unprecedented occurrence of hypoxia across the coastal zone of the Baltic Sea. We have identified 115 sites that have experienced hypoxia during the period 1955–2009 increasing the global total to ca. 500 sites, with the Baltic Sea coastal zone containing over 20% of all known sites worldwide. Most sites experienced episodic hypoxia, which is a precursor to development of seasonal hypoxia. The Baltic Sea coastal zone displays an alarming trend with hypoxia steadily increasing with time since the 1950s effecting nutrient biogeochemical processes, ecosystem services, and coastal habitat.

Defining reference conditions for coastal areas in the Baltic Sea

The overall aim of DEFINE is to provide a methodology to define reference conditions for nutrient concentrations in the coastal zone of the Baltic Sea. This will aid the national authorities that s ...

Impact of eutrophication and climate change on Cd and other trace metal dynamic in the Gulf of Riga, Baltic Sea

Abstract The ability of Cd and other trace metals to be incorporated in living phytoplankton cells has been widely used to explain its dynamic in marine ecosystem. However, the discrepancy between results from water column studies and those from studies in sediments remain unexplained. This strongly suggests a need for study with a more interconnected approach in identification of the main governing factors of trace element dynamics. Therefore, we conducted this study, which linked sedimentary records of trace elements with particular emphasis on Cd with available supporting information from sediments and water column. The concentrations of Cu, Mn, Cd and Cr in sediments of the Gulf of Riga exhibited significant (P < 0.01) positive relationships, while concentrations of Al and Ni had significant (P < 0.01 and P < 0.05, respectively) negative correlation with concentrations of TC. Concentrations of Zn, Pb and Fe in sediments did not exhibit significant correlation with concentrations of total carbon (TC). The vertical profiles of concentrations of several elements indicated that their accumulation patterns in sediments have changed substantially over time in respect to that of TC. The magnitude of change varied substantially from retaining positive correlation but changing element ratio value, in case of Cd, to complete shift from positive correlation to negative, in case of Zn and Cu. Abstract in Latvian Fitoplanktona spēja iesaistīt Cd šūnā ir plaši tikusi izmantota lai skaidrotu Cd dinamiku jūras ekosistēmās. Tai pašā laikā ir novērotas rezultātu atšķirības ūdenī un sedimentos, kuras līdz šim nav izskaidrotas. Tas nosaka nepieciešamību veikt pētījumu, kurā tiktu sasaistīti galvenie pēdu elementu dinamiku kontrolējošie faktori. Šajā pētījumā tika saistīts pēdu elementu vertikālais sadalījums sedimentos ar pieejamo atbalstošo informāciju no sedimentiem un ūdens kolonnu, īpašu uzmanību pievēršot Cd. Rīgas līča sedimentos novērotās Cu, Mn, Cd un Cr koncentrācijas uzrāda nozīmīgu (ANOVA < 0.01) pozitīvu korelāciju ar TC (kopējais ogleklis). Tai pašā laikā Al un Ni uzrāda nozīmīgu (ANOVA < 0.01) negatīvu korelāciju ar TC. Savukārt Zn, Pb un Fe koncentrācijas sedimentos neuzrāda nozīmīgu korelāciju ar TC. Vairāki no apskatītajiem elementiem skaidri parādīja, ka laika gaitā ir būtiski mainījušies to akumulācijas režīmi attiecībā pret TC akumulācijas režīmu. Izmaiņu lielums ir atšķirīgs atšķirīgiem elementiem.