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CURATOR
A pinboard by
Tiago Passos

Higher Degree by Research Student, The University of Sydney

PINBOARD SUMMARY

Moderating the global average temperature increase to less than 2°C as proposed in the Paris Agreement of December 2015 has motivated innovative approaches to reduce the concentration of greenhouse gases in the atmosphere. One technology proposed for carbon dioxide removal (CDR) in the atmosphere is ocean macronutrient fertilization (OMF) using the macronutrients nitrogen and phosphorus to increase marine biomass and subsequently carbon export through phytoplankton growth. Increasing primary production of the ocean is expected to increase carbon sequestration to the deep ocean as well as potentially enhancing the higher trophic levels of the marine food web. However, there is a gap in quantifying the amount of primary production that may be grazed by microzooplankton following macronutrient fertilization of the ocean. Microzooplankton grazing affects the transference of carbon into the marine food web. The present study aims to experimentally examine microzooplankton grazing before, during and after simulated OMF, in order to elucidate the fraction of primary production grazed by this predator class. A total of 3 experiments were conducted between January and April 2017 at a long term ocean monitoring site offshore of Sydney, Australia. The preliminary results on phytoplankton biomass show the difference made by microzooplankton grazing before and after ocean macronutrient fertilization.

6 ITEMS PINNED

Zooplankton predators and prey: body size and stable isotope to investigate the pelagic food web in a deep lake (Lake Iseo, Northern Italy)

Abstract: Seasonal changes in trophic position and food sources of deep subalpine lake (Lake Iseo, Northern Italy) zooplankton taxa were investigated during the year 2011. Furthermore, it's combined carbon and nitrogen Stable Isotope Analysis (SIA) with size-specific analyses of both, the major predatory cladoceran (Leptodora kindtii, Focke) and two potential preys (Daphnia longispina complex and Eubosmina longicornis). SIA studies have been extremely useful to track the energy flow through complex trophic network, however, if it is applied to analyze relation between two/few species may lead to misleading interpretations. In fact, integrating size-specificity allowed for understanding why L. kindtii nitrogen isotopic fingerprint fully overlapped with Daphnia, in spring. By investigating changes in L. kindtii's feeding basket, we found that in spring, L. kindtii mainly relied upon E. longicornis as prey, Daphnia being of too large body size for being captured by L. kindtii. Among preys encountered directly in front by a free-swimming Leptodora, only those able to fit into basket opening can be captured. As basket diameter increases with animal body length, size selection of prey depends on L. kindtii body length. As in other deep, subalpine lakes, E. longicornis was less 15N-enriched than Daphnia, most likely because of exploiting nitrogen fixing, cyanobacteria colonies, commonly detected in Lake Iseo with the onset of thermal stratification. Cyclopoid adults were at the top of zooplankton food chain and they could potentially be feeding on Daphnia. They, however, likely fed in a different habitat (>20 m deep water), as suggested by a rather than negligible carbon fractionation. The results overall suggest that size-specificity is crucial for addressing space and time changes in trophic links between organisms composing the two hierarchical levels within open water zooplankton community. Seasonal changes in trophic position and food sources of deep subalpine lake (Lake Iseo, Northern Italy) zooplankton taxa were investigated during the year 2011. Furthermore, it's combined carbon and nitrogen Stable Isotope Analysis (SIA) with size-specific analyses of both, the major predatory cladoceran (Leptodora kindtii, Focke) and two potential preys (Daphnia longispina complex and Eubosmina longicornis). SIA studies have been extremely useful to track the energy flow through complex trophic network, however, if it is applied to analyze relation between two/few species may lead to misleading interpretations. In fact, integrating size-specificity allowed for understanding why L. kindtii nitrogen isotopic fingerprint fully overlapped with Daphnia, in spring. By investigating changes in L. kindtii's feeding basket, we found that in spring, L. kindtii mainly relied upon E. longicornis as prey, Daphnia being of too large body size for being captured by L. kindtii. Among preys encountered directly in front by a free-swimming Leptodora, only those able to fit into basket opening can be captured. As basket diameter increases with animal body length, size selection of prey depends on L. kindtii body length. As in other deep, subalpine lakes, E. longicornis was less 15N-enriched than Daphnia, most likely because of exploiting nitrogen fixing, cyanobacteria colonies, commonly detected in Lake Iseo with the onset of thermal stratification. Cyclopoid adults were at the top of zooplankton food chain and they could potentially be feeding on Daphnia. They, however, likely fed in a different habitat (>20 m deep water), as suggested by a rather than negligible carbon fractionation. The results overall suggest that size-specificity is crucial for addressing space and time changes in trophic links between organisms composing the two hierarchical levels within open water zooplankton community.Leptodora kindtii,DaphnialongispinaEubosmina longicornisL. kindtiiDaphniaL. kindtiiL. kindtii E. longicornis DaphniaL. kindtii.LeptodoraL. kindtiiE. longicornis 15DaphniaDaphnia 

Pub.: 23 Sep '16, Pinned: 29 Aug '17

Morphological abnormalities in cladocerans related to eutrophication of a tropical reservoir

Abstract: In zooplankton communities, morphological changes in Cladocera (Crustacea: Branchiopoda) may be resulting from water pollution by anthropogenic activities and/or natural events. The removal of vegetation cover, urbanization, agriculture and sewage release accelerate the eutrophication process in the aquatic environment. The present study seeks to demonstrate the occurrence of morphological abnormalities in cladocerans and relate the changes in the morphology and species composition to the physical and chemical parameters of the water. Samplings were made monthly in five stations on the Sapucaí River compartment of Furnas Reservoir, located in the state of Minas Gerais, Brazil, from July 2013 to February 2014. The Furnas Reservoir has intense occupation of the surrounding areas by agriculture, urban and industrial activities and the installation of net cage fish cultures, which contribute to the water quality deterioration. Cladocerans samples were collected using a suction pump and plankton net (68 μm mesh size) and concentrated from a volume of 400 L. The measures of physical and chemical parameters of the water were obtained by a Horiba U-50 multi-sensor on the surface of water column and the density and morphology of Cladocera were made by microscopy. Twenty-three species of Cladocera were recorded with high organism densities of Chydoridae family species. Morphological abnormalities were observed in Daphnia gessneri, Ceriodaphnia silvestrii, Bosmina longirostris, Bosmina tubicen and Chydorus pubescens. The highest densities of C. pubescens with abnormalities were observed at sampling stations which had littoral characteristics and influences of sewage release. For C. pubescens, abnormalities were observed and classified into two types. The type 1 abnormality was considered an increase of length of intestine and size of its intestinal loop, whereas for type 2 was considered the occurrence of an intestine prolapse. The morphological abnormalities in cladocerans were described and compared to the ones described in the literature. From the results, it may observe that the abnormalities were probably resulting from continuous eutrophication process which has been occurring in the reservoir due to anthropogenic activities around the reservoir and a decrease in the water volume of the reservoir, caused by an unusual dry weather period in this region in the last years.In zooplankton communities, morphological changes in Cladocera (Crustacea: Branchiopoda) may be resulting from water pollution by anthropogenic activities and/or natural events. The removal of vegetation cover, urbanization, agriculture and sewage release accelerate the eutrophication process in the aquatic environment. The present study seeks to demonstrate the occurrence of morphological abnormalities in cladocerans and relate the changes in the morphology and species composition to the physical and chemical parameters of the water. Samplings were made monthly in five stations on the Sapucaí River compartment of Furnas Reservoir, located in the state of Minas Gerais, Brazil, from July 2013 to February 2014. The Furnas Reservoir has intense occupation of the surrounding areas by agriculture, urban and industrial activities and the installation of net cage fish cultures, which contribute to the water quality deterioration. Cladocerans samples were collected using a suction pump and plankton net (68 μm mesh size) and concentrated from a volume of 400 L. The measures of physical and chemical parameters of the water were obtained by a Horiba U-50 multi-sensor on the surface of water column and the density and morphology of Cladocera were made by microscopy. Twenty-three species of Cladocera were recorded with high organism densities of Chydoridae family species. Morphological abnormalities were observed in Daphnia gessneri, Ceriodaphnia silvestrii, Bosmina longirostris, Bosmina tubicen and Chydorus pubescens. The highest densities of C. pubescens with abnormalities were observed at sampling stations which had littoral characteristics and influences of sewage release. For C. pubescens, abnormalities were observed and classified into two types. The type 1 abnormality was considered an increase of length of intestine and size of its intestinal loop, whereas for type 2 was considered the occurrence of an intestine prolapse. The morphological abnormalities in cladocerans were described and compared to the ones described in the literature. From the results, it may observe that the abnormalities were probably resulting from continuous eutrophication process which has been occurring in the reservoir due to anthropogenic activities around the reservoir and a decrease in the water volume of the reservoir, caused by an unusual dry weather period in this region in the last years. Daphnia gessneriCeriodaphnia silvestriiBosmina longirostrisBosmina tubicenChydorus pubescens.C. pubescensC. pubescens

Pub.: 27 Oct '16, Pinned: 29 Aug '17

The pelagic habitat analysis module for ecosystem-based fisheries science and management

Abstract: We have developed a set of tools that operate within an aquatic geographic information system to improve the accessibility, and usability of remote-sensed satellite and computer-modeled oceanographic data for marine science and ecosystem-based management. The tools form the Pelagic Habitat Analysis Module (PHAM), which can be applied as a modeling platform, an investigative aid in scientific research, or utilized as a decision support system for marine ecological management. Applications include fisheries, marine biology, physical and biological oceanography, and marine spatial management. The GIS provides a home for diverse data types and automated tools for downloading remote sensed and global circulation model data. Within the GIS environment, PHAM provides a framework for seamless interactive four-dimensional visualization, for matching between disparate data types, for flexible statistic or mechanistic model development, and for dynamic application of user developed models for habitat, density, and probability predictions. Here we describe PHAM in the context of ecosystem-based fisheries management, and present results from case study projects which guided development. In the first, an analysis of the purse seine fishery for tropical tuna in the eastern Pacific Ocean revealed oceanographic drivers of the catch distribution and the influence of climate-driven circulation patterns on the location of fishing grounds. To support management of the Common Thresher Shark (Alopias vulpinus) in the California Current Ecosystem, a simple empirical habitat utilization model was developed and used to dynamically predict the seasonal range expansion of common thresher shark based on oceanographic conditions.

Pub.: 23 Jan '17, Pinned: 29 Aug '17