Phosphorus Contents Re-visited After 40 Years in Muddy and Sandy Sediments of a Temperate Lagoon System

Abstract

Worldwide, coastal water bodies suffer from anthropogenically elevated nutrient inputs, which led to eutrophication. Sediments in eutrophic systems are assumed to be an important internal nutrient source. The total phosphorus (TP) concentration (mg g −1 dry mass) is widely used as a proxy for the sediment nutrient load. 2-D distribution maps of TP concentrations are used for management plans, where areas of high TP values are marked in red. However, the sediment density is lowered at increasing water content, which can lead to different TP stocks per g m −2 . The aim of this study was, to do a re-evaluation of TP concentrations and stocks in the model ecosystem of the Darß-Zingst Bodden chain, a typical lagoon system of the southern Baltic Sea. Sediment cores were taken at eight stations along transects from shallow to deeper parts of the lagoon. Samples were analyzed for TP, water and organic content, as well as density. This data set was compared to results from a sediment survey during the time of highest nutrient inputs (40 years ago) at the same sampling stations. TP concentrations from 40 years ago and today were in the same range. The highest TP concentrations (up to 0.6 mg TP g −1 dry mass) were found in the deeper basins and lowest concentrations in the shallow areas of the lagoon (down to 0.05 mg TP g −1 dry mass). However, normalization over dry bulk density (DBD) reversed some results. The highest TP stocks (up to 5 g TP m −2 ) were then found in the shallow areas and lowest stocks (down to 0.2 g TP m −2 ) in the deeper parts of the lagoon. Some stations did not exhibit any differences of TP at all, even after including the DBD. These findings suggest that there seems to be no up-, or downward trend in nutrient concentrations of sediments even after 25 years of reduced external nutrient inputs. Furthermore, TP stocks point to possible diffuse P entry pathways that counteract external nutrient reductions. These findings can have an impact on possible countermeasures for ecosystems rehabilitation, like sediment removal or nutrient reductions in the adjacent land.

Seasonal Variation in Biomass and Production of the Macrophytobenthos in two Lagoons in the Southern Baltic Sea

“…In the early 1980ies, eutrophication caused a collapse of the macrophytobenthos in the entire DZBC which became dominated by the pelagic producers (Schiewer, 1998). Lagoons of the Baltic Sea receive nutrients from diffuse run-offs (Berthold et al, 2018b), atmospheric wet and dry deposition (Berthold et al, 2019) and from sediment (Bitschofsky, 2016;Berthold et al, 2018c). In 1990, new wastewater treatment plants reduced the discharge of P and N in the lagoons of the German Baltic Sea by over 89% (Nausch et al, 2011).…”

Disintegration half-life of biodegradable plastic films on different marine beach sediments

“…Phosphorous concentrations from all sites were low compared to a study in the Mediterranean Sea in Turkey ( Gunduz et al, 2011 ). The relatively higher concentration of phosphorous in sediment from Portoferraio, the largest town on the island, probably resulted from sewage or industrial effluents ( Berthold et al, 2018 ; Howell, 2010 ). Also, Marina di Campo is a small town with more inhabitants than the villages Fetovaia and Naregno, therefore an anthropogenic impact on the bacterial abundance or activity is probable and could explain the faster disintegration.…”

Dynamics of primary productivity in relation to submerged vegetation of a shallow, eutrophic lagoon: a field and mesocosm study

“…The surprising findings of overall constant net-heterotrophy within the ecosystem and the shallow mesocosms can be explained by high amounts of waterborne POC (up to 16 mg L -1 ) and DOC (up to 12 mg L -1 ), stimulating bacterial turnover (up to 18 μg C L -1 h -1 , [49]) and probably respiration. Furthermore, sediments in the ZS and elsewhere in the DZLS can show combustible organic contents of up to 20% [50], indicating another oxygen sink in the system. A strong light gradient may result in net-heterotrophy already in shallow areas.…”

“…Furthermore, phytoplankton grew throughout the year in the shallow areas in proximity to the reed belt and possible P runoff of the DZLS, whereas there was only minor growth in deeper lagoon parts [11]. P stocks in the sediment were described to be highest in shallow areas [50], probably caused by large macrozoobenthos populations [60] who may increase nutrient burial through two- to three-fold increased sediment-water contact zones [61]. These results indicate that new production is generated in the shallow regions of eutrophic lagoons with high turn-over rates, instead of the whole turbid ecosystem.…”