Manganese content records seasonal upwelling in Lake Tanganyika mussels

Abstract

Abstract. Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of cold, oxygendepleted, nutrient-rich deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a three-year-long limnological and geochemical survey of the coastal waters performed on the dissolved and particulate fractions were compared to LA-ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Three shells present very similar Mn/Ca profiles dominated by a peak that matched the concomitant increase of Mn and chlorophyll a in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8 Mn/Ca peaks suggesting at least an 8-year-record of seasonal changes in water composition. We postulate that Mn/Ca in shells record the conjunction of an increase of biological activity with supplied of dissolved Mn and nutriments in coastal waters, resulting in an enhanced assimilation of biogenic Mn-rich particles. By combining the most recent generation of laser ablation system and the powerful High Resolution ICP-MS, the spatial resolution could be improved down to 5 to 10 µm crater size and end up in a better constrain of the relative variations of the annual Mn peaks. Such an approach on P. spekii from Lake Tanganyika has definitively a great potential to provide recent and past records on primary productivity associated with the monsoon climate system.

Trace element composition of freshwater pearl mussels Margaritifera spp. across Eurasia: Testing the effect of species and geographic location

“…Very high values may be related to spikes in phytoplankton productivity and Mn oxy(hydr)oxide formation within the microenvironments produced by phytoplankton such as pelagic algal clumps (Richardson et al, 1988). This particular manganese may be further consumed by the bivalves (i.e., Langlet et al, 2007). For example, Nystrom et al (1996) observed Mn peaks in A C C E P T E D M A N U S C R I P T…”

Farming and/or foraging? New environmental data to the life and economic transformation of Late Neolithic tell communities (Tisza Culture) in SE Hungary

“…Some of the routinely recorded trace elements in shells are excellent markers or proxies of certain parameters of the studied waterways. Mn 2þ has been proposed as indicator of algal productivity (Vander Putten et al, 2000;Langlet et al, 2006Langlet et al, , 2007Caroll and Romanek, 2008;Siegele et al, 2001;Lazareth et al, 2003) and as such an ideal proxy of the rate of dissolved oxygen in the water (Mutvei and Westermark, 2001;Ravera et al, 2003Ravera et al, , 2007Caroll and Romanek, 2008). Fe 2þ , Zn 2þ are soluble in relation to the acidity of the medium and as such may record fluctuations in the pH (Stumm and Morgan, 1996;Mutvei and Westermark, 2001).…”

Effects of Pollution on Freshwater Organisms

“…Frank and Gerstmann (2007) hypothesized that the decline in freshwater pearl mussels (Margaritifera margaritifera) throughout Europe is due to pollutants that affecting calcium metabolism, resulting in brittle shells. Langlet et al (2007) proposed using the shell of the freshwater bivalve, Pleiodon spekii, as a geochemical archive to assess seasonal changes of Lake Tanganyika, Africa. Ravera et al (2007) assessed the impact of lake trophy on trace element accumulation by comparing two different populations of freshwater mussels (Unio pictorum mancus).…”