1,721,092 research outputs found
The future of the past: Applications of paleoecological findings in peatland restoration in Indonesia
No full textEleven month high resolution pollen and spore sedimentation record off SW Java in the Indian Ocean
No full textSettling particles collected in a sediment trap 60 km off SW Java in the Indian Ocean at a 2200 m deep site, about 830 m above the sea floor, between December 2001 and November 2002 (intervals of 16 days for 11 months) were analyzed for the abundance and taxa composition of pollen and spores. Several factors control their deposition such as the monsoon-driven reversal of the wind directions and ocean currents as well as flowering periods. Long distance transport plays a particular role during the monsoon seasons. During the NW monsoon (mid-December-beginning of March), maxima of Picea type, Alnus, Pinus and Quercus pollen occur in the trap samples, which correspond to wind and marine currents coming from the north, probably the Equatorial Counter Current and Southern Java Current, transporting pollen from the southern part of continental Asia and Sumatra to the research area. During the SE monsoon (end of July-mid-November), an increase of pollen originating from southeast Indonesia and Australia was observed. Pollen grains were probably transported by the South Equatorial Current and partly by the Leeuwin Current. Casuarina and, in part, Eucalyptus are most abundant during this period. During the intermonsoon period, assemblages are mainly composed of pollen originating from West Java. Maxima of some pollen taxa, such as Elaeocarpus, Myrica, Dacryccupus type, Casuarina, Eucalyptus and Podocarpus type probably reflect their flowering periods. The transportation time from the pollen source area to the sediment trap is about 1-2 months. The extrapolated pollen accumulation rate of the marine sediment trap would be about 1670 grains/cm(2)/yr. The trap collected low concentrations of mangrove pollen, which might be the result of the strong destruction of the mangrove belt in Java during recent decades. High values of Poaceae pollen are probably related to the land use, forest canopy opening and development of the secondary vegetation in West Java. The majority of the pollen and spores collected by the sediment trap reflects the vegetation of SW Java, but long distance transport, in particular by the marine currents during the SE and NE monsoons, needs to be considered when interpreting marine pollen records off SW Java in the eastern Indian Ocean. (C) 2014 Elsevier B.V. All rights reserved
Two-step vegetation response to enhanced precipitation in Northeast Brazil during Heinrich event 1
No full textHigh resolution palynological and geochemical data of sediment core GeoB 3910-2 (located offshore Northeast Brazil) spanning the period between 19 600 and 14 500 calibrated year bp (19.6-14.5 ka) show a land-cover change in the catchment area of local rivers in two steps related to changes in precipitation associated with Heinrich Event 1 (H1 stadial). At the end of the last glacial maximum, the landscape in semi-arid Northeast Brazil was dominated by a very dry type of caatinga vegetation, mainly composed of grasslands with some herbs and shrubs. After 18 ka, considerably more humid conditions are suggested by changes in the vegetation and by C(org) and C/N data indicative of fluvial erosion. The caatinga became wetter and along lakes and rivers, sedges and gallery forest expanded. The most humid period was recorded between 16.5 and 15 ka, when humid gallery (and floodplain) forest and even small patches of mountainous Atlantic rain forest occurred together with dry forest, the latter being considered as a rather lush type of caatinga vegetation. During this humid phase erosion decreased as less lithogenic material and more organic terrestrial material were deposited on the continental slope of northern Brazil. After 15 ka arid conditions returned. During the humid second phase of the H1 stadial, a rich variety of landscapes existed in Northeast Brazil and during the drier periods small pockets of forest could probably survive in favorable spots, which would have increased the resilience of the forest to climate change
Intertwined effects of climate and land use change on environmental dynamics and carbon accumulation in a mangrove‐fringed coastal lagoon in Java, Indonesia
No full textThe identification and quantification of natural carbon (C) sinks is critical to global climate change mitigation efforts. Tropical coastal wetlands are considered important in this context, yet knowledge of their dynamics and quantitative data are still scarce. In order to quantify the C accumulation rate and understand how it is influenced by land use and climate change, a palaeoecological study was conducted in the mangrove‐fringed Segara Anakan Lagoon (SAL) in Java, Indonesia. A sediment core was age‐dated and analyzed for its pollen and spore, elemental and biogeochemical compositions. The results indicate that environmental dynamics in the SAL and its C accumulation over the past 400 years were controlled mainly by climate oscillations and anthropogenic activities. The interaction of these two factors changed the lagoon's sediment supply and salinity, which consequently altered the organic matter composition and deposition in the lagoon. Four phases with varying climates were identified. While autochthonous mangrove C was a significant contributor to carbon accumulation in SAL sediments throughout all four phases, varying admixtures of terrestrial C from the hinterland also contributed, with natural mixed forest C predominating in the early phases and agriculture soil C predominating in the later phases. In this context, climate‐related precipitation changes are an overarching control, as surface water transport through rivers serves as the “delivery agent” for the outcomes of the anthropogenic impact in the catchment area into the lagoon. Amongst mangrove‐dominated ecosystems globally, the SAL is one of the most effective C sinks due to high mangrove carbon input in combination with a high allochthonous carbon input from anthropogenically enhanced sediment from the hinterland and increased preservation. Given the substantial C sequestration capacity of the SAL and other mangrove‐fringed coastal lagoons, conservation and restoration of these ecosystems is vitally important for climate change mitigation
Late Holocene ENSO-related fire impact on vegetation, nutrient status and carbon accumulation of peatlands in Jambi, Sumatra, Indonesia
No full textHigh-resolution multi-proxy reconstruction of environmental changes in coastal waters of the Java Sea, Indonesia, during the late Holocene
No full textMenschliche Einflussgrößen auf das Pamba-Becken (Kerala, Indien) und ihre Auswirkungen auf das Ökosystem des südlichen Vembanad Ästuars - eine Wasserscheidenbetrachtung.
No full textAnthropogenic inputs nowadays are the major source of nutrients leading to cultural eutrophication in the coastal aquatic systems. While river inputs of anthropogenic nutrients into coastal seas is considered a global problem, the database is biased towards temperate regions, developed countries and major river systems. Little is known on the amount and composition of nutrient fluxes from densely populated catchments in tropical regions and, in particular from small- and medium-sized rivers. The South Indian Pamba River is a prime example in this respect because of its manifold human interventions such as the Sabarimala pilgrimage, the largest pilgrim centre in the world, agricultural practices and sewage disposal. The goals of this study were (i) to define cause-effect relationships by assessing the effect of various human interventions such as the pilgrims, agriculture and sewage disposal in combination with the seasonal variations in hydrology on the nutrients and organic matter composition (ii) to quantify land use specific nutrient inputs (iii) to assess the respective impacts in the Pamba River and (iv) to understand the ecological consequences in the Vembanad estuary. The Pamba River and the Vembanad estuary were sampled from March 2010 to February 2012. 9 sampling campaigns were carried out to cover the south west monsoon (SWM, May/June 2010), north east monsoon (NEM, October to December 2011) and pre monsoon (PM, March/April 2010 and January/February 2012). A socioeconomic survey on agricultural practices was conducted to collect information on the type, time and quantity of fertilizer application during November 2011. Dissolved organic nitrogen (DON) was the dominant form of N and accounted for 99% of the total dissolved nitrogen (TDN) pool in the Pamba River. Land use specific cause-effect relationships were identified for the Pamba catchment. The global maximum DON concentration (29,302 µM) and yield (745 kg ha-1 yr-1) in the Pamba River were due to the pilgrim activities, high population density, agricultural and livestock farming as well as the lack of infrastructure for sanitation facilities. Domestic sewage inputs (26 kg ha-1 yr-1) introduced into the Pamba catchment was an order of magnitude higher than the other human impacted world rivers. Dissolved inorganic nitrogen (DIN) was dominated by ammonium (NH4 ) due to the effluents from pilgrim activities in the upstream temple region, while nitrate (NO3-) was the major N species in the downstream agriculture segments. DIN yields in the Pamba River were lower in agriculture segments with systematic fertilizer management, i.e. in the paddy and rubber dominated regions, than in the settlement with mixed tree crop (SMT) regions where farmers tend to apply more fertilizer than required by the plants because of a lack of knowledge. Annual NPK fertilizer inputs in the catchment were 95 kg ha-1 yr-1, of which 13% of total N as DIN and 1% of phosphate-P reached the river mouth. The average yield for the Pamba catchment amounted to 3.5 kg ha-1 yr-1 of DIN and 0.2 kg ha-1 yr-1 of phosphate-P (PO43--P). Seasonal variations in hydrology exhibited marked changes in the dissolved nutrients and organic matter loading in the Pamba River, i.e. the loads were high during the SWM and NEM compared to the PM. Suspended organic matter were mainly composed of planktonic as indicated by high chlorophyll a values (0.7 to 34.2 µg L-1) and terrestrial sources in the Pamba River. High nutrient concentrations were observed in the Vembanad estuarine region receiving direct inputs from the upstream catchments, thereby exhibiting signs of eutrophication. Phytoplankton abundance was high in the upper estuary and ranged between 1,513 to 3,552 cells L-1 and < 900 cells L-1 in the mid and lower estuary. Uptake by the phytoplankton and water hyacinth (Eichhornia sp.) in the Vembanad estuary were the major sink of the nutrients in the Vembanad estuary. From this study it is evident that the lack of technological investments not only affects the drinking water and river biodiversity, but also has a huge impact on the riverine nutrient concentrations. These results suggest that installation of adequate sanitation measures for waste disposal and treatment together with improved agricultural and animal management practices could strongly reduce the anthropogenic nutrient inputs into the Pamba River and in turn leads to less impact in the receiving Vembanad estuary. This study also underscores the need for more regional scale quantitative studies from densely-populated tropical river catchments in order to improve global nutrient budgets and the assessment of the consequences of anthropogenic nutrient inputs into coastal aquatic systems
Einfluss von Zuckerrohrmonokultur auf die Biogeochemie und Phytoplanktondynamik in der Mundau Manguaba Lagune und dem Fluss Paraiba do Sul in Brasilien
No full textSugar cane cultivation has become the main land use in northeast and southeast Brazil and it is still increasing because of a growing national and international demand of sugar and biofuel. Shallow coastal lagoons and estuaries are the linkage between terrestrial and marine environments and are susceptible to anthropogenic modifications. Little is know about the impact of sugar cane cultivation in these systems. Aim of this study was to gain knowledge on the impact of effluents from sugar cane cultivation on the biogeochemistry and phytoplankton dynamics in two shallow coastal systems affected by sugar cane monoculture in their watersheds, a coastal lagoon and an estuary in Brazil. In the Mundau Manguaba Lagoon (MML), water samples were collected at the beginning and end of the dry season during five expeditions between September 2007 and February 2009. Additionally, sediment cores were taken in March 2007. In the Paraiba do Sul River (PSR), samples were taken during the rainy (January) and dry (September) season 2008. The main elements of this study were the determination and characterization of nutrients (nitrate, nitrite, ammonium, silicate, phosphate) and total suspended matter (TSM) as well as phytoplankton communities in the MML and the PSR. Particulate organic matter (Corg, PN) and stable carbon and nitrogen isotopes (13C, 15N) were determined in TSM of surface water in the MML and PSR and sediments of the MML. Inorganic nutrients were measured in the water samples. Phytoplankton abundance, biomass and community composition were identified in the MML. Effects of nutrient enrichment caused by fertilizer runoff from sugar cane fields on phytoplankton communities in the MML were experimentally simulated. Chlorophyll a (chl a) was used to estimate phytoplankton biomass in the PSR. Nutrients and organic matter derived from fertilizer runoff in the catchment area of the PSR were transported from the river and its tributaries to the estuary and subsequently to adjacent coastal waters during the rainy season because of high river discharge. Reduced river discharge and long residence time during the dry season led to an increase in chl a amount and retention of allochthonous and autochthonous material inside the system. Nutrient concentrations in the MML were mainly governed by the rivers which drain the sugar cane dominated catchment area. A seaward nutrient decrease coincided with high phytoplankton biomass inside the lagoons and was the result of fast nutrient uptake by algae. Parts of the organic matter were removed from the water column due to sedimentation and were recycled or stored in the sediments of the lagoons. Other parts of the organic matter were exported from the Manguaba and Mundau lagoons into adjacent coastal waters due to tidal currents. Phytoplankton community and diversity were highly variable in both lagoons because of rapidly changing salinity and nutrient concentrations as well as residence time. Thus, temporal and spatial phytoplankton distributions and shifts between cyanobacteria and diatom dominated communities were observed in the MML. Nutrient enrichment experiment conducted in order to simulate high nutrient input from fertilizer runoff showed a direct response of phytoplankton communities. Diatoms were the main profiteers due to permanently high silicate concentrations in tropical aquatic ecosystems. Alterations in the nutrient ratios affected by high nitrogen and phosphate inputs from sugar cane cultivation lead to a shift in phytoplankton communities and consequently influence the entire food web dynamics in the lagoons. It can be concluded that lagoons and estuaries play an important role for nutrient and organic matter cycles in the coastal ecosystems affected by sugar cane cultivation in the northeast and southeast regions of Brazil. Seasonal variations in fertilizer runoff, geomorphology of the system and biological processes are the main factors that control the material distribution, composition and finally the retention of nutrients and organic matter inside the system or the outwelling from the system into adjacent coastal waters
Nutrients in Kenya's Coastal Waters: Analyzing Sources, Pathways, and Ecological Implications
No full textCoastal ecosystems face increasing nutrient enrichment from human activities, threatening ecological health globally. This PhD study assessed anthropogenic nutrient dynamics in Kenya’s coastal waters, focusing on their influence on phytoplankton shifts and harmful algal bloom (HAB) risks. Combining field surveys, lab analyses, and literature reviews (August 2021–July 2022), the research revealed elevated nutrient levels in urban-adjacent estuaries like Tudor Creek, with seasonal peaks linked to freshwater influx. A shift from nitrogen-limited to dissolved inorganic nitrogen (DIN)-enriched conditions was observed, with phosphorus/silica becoming limiting. Nutrient sources included sewage, agriculture, industry, submarine groundwater, and atmospheric deposition. Despite identifying 59 harmful microalgae taxa (47% toxin-producing), no phytotoxins were detected. Findings confirm nutrient enrichment drives phytoplankton community changes, favoring HAB species. The study underscores the urgent need for integrated nutrient management to safeguard Kenya’s coral reefs, seagrass, and marine biodiversity
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