SILVA, Merivalda Doroteu da. Diagnóstico da comunidade fitoplanctônica de um reservatório no semiárido nordestino. 2013. 112 f. Dissertação (Mestrado em ecologia e recursos naturais)- Universidade Federal do Ceará, Fortaleza-CE, 2013. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-05-24T19:00:24Z No. of bitstreams: 1 2013_dis_mdsilva.pdf: 2196222 bytes, checksum: 8caacc5815049dd42cc980d19e7aa74e (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-05-27T20:41:02Z (GMT) No. of bitstreams: 1 2013_dis_mdsilva.pdf: 2196222 bytes, checksum: 8caacc5815049dd42cc980d19e7aa74e (MD5) / Made available in DSpace on 2016-05-27T20:41:02Z (GMT). No. of bitstreams: 1 2013_dis_mdsilva.pdf: 2196222 bytes, checksum: 8caacc5815049dd42cc980d19e7aa74e (MD5) Previous issue date: 2013 / In the semiarid region of Brazil, in addition to water deficit, another serious problem of water availability is limiting water quality due to eutrophication, resulting from the use and occupation of space in the vicinity of water bodies and contributions in the areas of the reservoirs. This study was conducted at Oros reservoir in the state of Ceará which is inserted in the Brazilian semiarid region. This research aimed to study the variability of phytoplankton community and the quality of surface water reservoir Orós, between the years 2008 to 2011, identifying the dynamics of the class with the highest frequency and the most abundant species of cyanobacteria existing in these waters and their potential health risk humana.Para answer this question were performed in the range 17 bimonthly collection campaigns in seven points of the tank the following limnological parameters (chlorophyll a, transparency, total phosphorus, nitrate, temperature and pH), totaling 714 samples (17 campaigns x 7 x 6 points parameters). Transparency measures, temperature, and pH was performed in the field, while the other samples for analysis were collected directly in water 30 cm deep, placed in vials previously washed and decontaminated (polyethylene and amber glass) and kept refrigerated in coolers to the site analysis. According to the results of chlorophyll concentrations increased over the four years of study, but are still in line with the standards of CONAMA, which allows up 30μg.L-1 to class 2. It is observed that the increase of the mean attribute with time, whereas the opposite happens for transparency. With respect to nutrients, phosphorus has gradually increased, with a slight decline in 2010, when there was less precipitation and consequently a low runoff, the same can be observed for the nitrate values. The average water temperature was between 28 ° C and 30 ° C, indicating that the Oros has warm waters, characteristics of semiarid regions. The values of pH may be noted that were always alkaline soil because this environment is rich in bicarbonate ions. The phytoplankton composition was composed by Chlorophyceae, Cyanophyceae, Bacillariophyceae, Euglenophyceae, xantophyceae and Zygnemaphyceae, especially with larger Chlorophyceae and Cyanophyceae species despite the smaller number of species quantities of individuals were always higher than the other groups of individuals. The frequency of the cyanobacteria group arrived between 50 and 60% of the samples collected. Were also carried out quantitative and qualitative analyzes of the cyanobacterial group, and this group was the one that prevailed during the study period and more worrying is that most of his subjects are potentially toxic. It was observed that the amounts of cells were always higher than the amounts stipulated by CONAMA Resolution N°. 357/2005. When there was the abundance of species of cyanobacteria could be observed that the species Aphanocapsa sp. was most abundant in the first three years, but was replaced in 2011 by Planktotrix agardhii, since both species are considered in the literature as potentially toxic. The diversity decreased over the years, inferring that this reservoir is in a state of eutrophication. / O estudo foi realizado no reservatório Orós, localizado no estado do Ceará o qual está inserido na região semiárida brasileira. Esta pesquisa teve por objetivo estudar a comunidade fitoplanctônica e a variabilidade da qualidade das águas superficiais do reservatório Orós, entre os anos de 2008 à 2011, identificando a dinâmica das classes de maior frequência, bem como as espécies de cianobactérias mais abundantes existentes nessas águas e seu potencial de risco à saúde humana. Realizou-se em intervalo bimestral 17 campanhas de coleta em sete pontos do reservatório dos seguintes parâmetros limnológicos (Clorofila a; transparência; fósforo total; nitrato; temperatura e pH), perfazendo um total de 714 amostras (17 campanhas x 7 pontos x 6 parâmetros). As medidas de transparência, temperatura, bem como o pH foi realizada em campo, enquanto as demais amostras para análise foram coletadas diretamente na água a 30 cm de profundidade, acondicionadas em frascos previamente lavados e descontaminados (polietileno e vidro âmbar) e mantidas resfriadas em caixas térmicas até o local de análises. De acordo com os resultados as concentrações de clorofila aumentaram ao longo dos quatro anos de estudos, porém ainda se encontram em consonância com os padrões do CONAMA, que permite até 30µg.L-1 para a classe II. Observa-se o aumento das médias desse atributo com o tempo, enquanto que ocorre o oposto para a transparência. Com relação aos nutrientes, o fósforo possui um aumento gradativo, tendo uma leve queda em 2010, quando houve menor precipitação e consequentemente um baixo escoamento superficial, o mesmo pode-se observar para os valores de nitrato. A temperatura média da água esteve entre 28 °C e 30 °C, indicando que o Orós possui águas quentes, características de regiões semiáridas. Quanto aos valores de pH pode-se notar que sempre estiveram alcalinos, devido o solo deste ambiente ser rico íons de bicarbonato. A composição do fitoplâncton foi composta por chlorophyceae, cyanophyceae, bacillariophyceae, euglenophyceae, xantophyceae e zygnemaphyceae, destacando-se chlorophyceae com maior número de espécies e cyanophyceae apesar do número menor de espécies as quantidades de indivíduos foram sempre superiores aos indivíduos dos outros grupos. A frequência do grupo de cianobactérias chegou entre 50 e 60% das amostras coletadas. Também foramam realizadas as análises quantitativa e qualitativa do grupo de cianobactérias, sendo que este grupo foi o que predominou durante o período de estudo e o mais preocupante é que grande parte de seus indivíduos são potencialmente tóxicos. Pôde-se observar que as quantidades de células sempre foram superiores as quantidades estipuladas pela resolução CONAMA n°357/2005. Quando realizou-se a abundância das espécies de cianobactérias pôde-se observar que a espécie Aphanocapsa sp. foi mais abundante nos três primeiros anos, porém foi substituída em 2011 pela Planktotrix agardhii, sendo que ambas as espécies são consideradas pela literatura como potencial tóxico.

Made available in DSpace on 2014-06-11T19:27:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-06-30Bitstream added on 2014-06-13T20:56:22Z : No. of bitstreams: 1 lachi_gb_me_jabo.pdf: 215317 bytes, checksum: eb1819efbb518f65960adda7fbccbf9f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O estudo foi realizado em um viveiro de criação semi-intensiva de peixes do Centro de Aqüicultura da UNESP (CAUNESP) Jaboticabal, SP. O trabalho avaliou algumas variáveis limnológicas e fitoplâncton neste viveiro utilizado para irrigação. Foram analisados variáveis físicas e químicas (pH, oxigênio dissolvido, condutividade, temperatura, alcalinidade total, formas de carbono inorgânico, dureza, sólidos totais solúveis, demanda bioquímica de oxigênio, nitrito, nitrato, amônia, fósforo total e ortofosfato), clorofila-a e identificação dos organismos fitoplanctônicos. A temperatura sofreu influência direta das condições ambientais. A utilização deste viveiro para fins de irrigação deve ser reavaliado em função das condições de manejo e da presença de Cyanobacteria. Devido a distribuição em série em que o viveiro estudado esta incluído, provocou o aumento nas variáveis limnológicas, principalmente no período de engorda dos peixes. O manejo inadequado em piscicultura geralmente acelera o processo de eutrofização, deteriorando a qualidade da água, em função do manejo empregado principalmente, pela administração de altas doses de ração e fertilização (orgânica ou inorgânica). O objetivo do trabalho foi avaliar alguns aspectos bióticos e abióticos de um viveiro de piscicultura e sua relação direta na qualidade da água para uso múltiplo. / This study was carried out at one semi-intensive breeding fishpond at the UNESP (CAUNESP) Aquaculture Center, in Jaboticabal, SP. The study evaluated some limnological parameters and phytoplankton of a fishpond used to irrigation. The purpose of this work was to determine physical and chemical variables (pH, dissolved oxygen, conductivity, temperature, total alkalinity, forms of inorganic carbon, hardness, total solids soluble, biochemical oxygen demand, nitrite, nitrate, ammonia, total phosphorus, and orthophosphate), chlorophyll-a and phytoplankton organisms consist. The temperature was influenced directly by climatic conditions. The utilization of this fishpond as a source of irrigation must be revaluated in function of management conditions and the presence of Cyanobacteria. In function of set up sequentially, this fishpond study had favored a change in the limnological features, mainly in the grow-out fish period. The used of inappropriate management may eventually produce the eutrophication, and water quality degradation due to the higher rates of ration and fertilizer (organic or inorganic). The present work was conducted to evaluate the biotic and abiotic aspects in the water quality of fish pond with water flow and distributed sequentially and multiple use.

Mesozooplankton community structure in the vicinity of the Prince Edward Islands (PEIs) was investigated during six surveys conducted in late austral summer (April/May), 1996 to 1999. Each year zooplankton samples were collected with a bongo net (300 µm mesh) at stations upstream (west), between and downstream (east) of the islands. Chlorophyll a concentrations were determined fluorometrically, corresponding with each net tow. The positions of the Subantarctic Front (SAF) and the Antarctic Polar Front (APF), in relation to the islands in the upstream region, were determined by a line of CTD and/or XBT stations. Both the SAF and the APF were characterised by a high degree of meridional variation in position. Changes in position of the fronts were shown to occur very rapidly. In 1999 the APF moved southwards by ~40nm and the SAF northwards by ~60nm in a period of two weeks, while in 1996 the SAF appeared to move ~120nm northwards in a two week period. The positions of the SAF and APF appeared to have a significant impact on phytoplankton biomass in the vicinity of the PEIs, through the alteration of local flow dynamics. Water retention in 1996, associated with the location of the SAF and APF far to the north and south of the PEIs respectively, corresponded with high chlorophyll a concentrations in the inter-island region (reaching 1.54 mg.m^(-3)). When the fronts were close to the islands, in 1997 and 1999, and a flow through environment existed, chlorophyll a concentrations in the inter-island region were comparatively low. Although biomass enhancement was only observed at the SAF in 1996, phytoplankton size structure in 1999 indicated that, when close to the PEIs, frontal production may be transported to the island system. This is potentially an important source of allochthonous input into the island system. Zooplankton assemblages were a mix of sub-Antarctic and Antarctic communities, with a weak presence of sub-tropical species. Cluster analysis showed that during each survey the region in the vicinity of the PEIs was divided into different, spatially separated zooplankton communities, associated with water masses of different origins. These communities were identified by variations in the abundance and biomass of species rather than variation in species composition and, in general, there was a relatively high degree of similarity both within and between surveys. Inter-annual community analysis revealed that, in many cases, there was greater similarity between communities from different years than communities within years, indicating that short-term variability exceeded inter-annual variability. Multiple regression analysis showed that the major correlate with zooplankton community structure during all surveys was sea temperature, accounting for as much as 77% of the variation in community structure. Temperature was indicative of the relative contribution of sub-Antarctic and Antarctic communities, with low temperatures being characterised by an increased predominance of Antarctic communities and vice versa. The differentiation between sub-Antarctic and Antarctic waters, and their respective communities, was particularly pronounced when the SAF and APF were in close proximity to the islands. Surface salinity and sounding had limited effect on community structure. The affect of sounding was intrinsically related to zooplankton interaction with the island ecosystem. Predation by the islands' land based predators and benthic fish appears to decrease zooplankton biomass over the island shelf, particularly the macrozooplankton size fraction. However, this may only be an important factor under conditions of water retention when replenishment of zooplankton stocks is low. The low densities of many macrozooplankton species, and other deep migrators, on the island shelf may be due to their limited advection onto shallow topography. By contrast, there are indications that zooplankton species occurring at shallower depths may be concentrated in the inter-island region by mesoscale flow patterns. Analysis of the population structure of the copepod Calanus simillimus showed that this species occurred at different stages in its life cycle during different years, even though sampling took place in the same calendar months, indicating that there was inter-annual variation in the timing of the biological season. Differences in the population structure of species, and consequently their contribution to abundance and biomass, may therefore have been an important contributor to inter-annual variation in community structure. Evidence is provided for a long-term trend of southward movement of the SAF. This may have a significant affect on the PEI ecosystem, increasing the proportion of allochthonous input and altering the tropho-dynamics of the island ecosystem

No description available.

The aim of the present study was to assess the ecological role of the euthecosome pteropod, Limacina retroversa, in particular, and the mesozooplankton community, in general, in the pelagic ecosystem of the Polar Frontal Zone (PFZ), Southern Ocean. Data were collected from four oceanographic surveys to the Indian sector of the PFZ during austral autumn 2000, 2002, 2004 and 2005. Copepods, mainly Calanus simillimus, Oithona similis, Clausocalanus spp. and Ctenocalanus spp., typically dominated total mesozooplankton counts, accounting for, on average, between 75.5 % and 88.1 % (Mean = 77.4 %; SD = 13.4 %) of the total, during the present investigation. Results of the study indicate that L. retroversa may, at times, contribute substantially to total mesozooplankton abundances. During the study, L. retroversa contributed between 0.0 and 30.0 % (Mean = 5.3 %; SD = 7.1 %) to total mesozooplankton numbers. Significant small-scale variability in abundance and size structure of L. retroversa and abundance of copepods was minimal. Inter-annual variability, on the other hand, was significant between some years. Total pteropod numbers were greatest during April 2002 and 2004, while copepods exhibited greatest abundances during April 2004 only. Pearson’s Correlation analysis suggested that L. retroversa abundances were positively correlated to total surface chlorophyll-a (chl-a) concentrations. The significantly lower chl-a concentrations recorded during April 2005 may explain the reduced pteropod numbers observed during that survey. The size class structure of L. retroversa comprised mainly small and mediumsized individuals during all four surveys. This corresponds well with records from the northern hemisphere (sub-Arctic and Arctic waters) where Limacina spp. are reported to exhibit maximum spawning during mid to late-summer. Higher abundances of large individuals only occurred during April 2005, when chl-a concentrations were very low; possibly the result of delayed spawning, due to reduced food availability. Ingestion rates of the four most abundant copepods, determined using the gut fluorescence technique, ranged between 159.32 ng (pigm) ind⁻¹ day⁻¹ and 728.36 ng (pigm) ind⁻¹ day⁻¹ (Mean = 321.01 ng (pigm) ind⁻¹ day⁻¹; SD = 173.91 ng (pigm) ind⁻¹ day). Ingestion rates of L. retroversa were much higher, ranging from an average of 4 28.68 ng (pigm) ind⁻¹ day⁻¹ in April 2002 to 4 196.88 ng (pigm) ind⁻¹day⁻¹in April 2005 (Mean = 4157.36 ng (pigm) ind⁻¹ day⁻¹; SD = 35.37 ng (pigm) ind⁻¹day⁻¹). Average daily grazing rates for the pteropod varied between 0.39 mg (pigm) m⁻² day⁻¹ in April 2005 and 17.69 mg (pigm) m-2 day-1 in April 2004 (Mean = 6.13 mg (pigm) m⁻² day⁻¹; SD = 11.04 mg (pigm) m⁻² day⁻¹); corresponding average daily grazing impacts ranged between 8.4 % and 139.8 % of the phytoplankton standing stock in April 2005 and 2004, respectively (Mean = 48.5 %; SD = 84.5 %). Average daily grazing rates of the four copepods ranged from 4.58 mg (pigm) m⁻² day⁻¹ to 8.77 mg (pigm) m⁻² day⁻¹ -1, during April 2002 and 2004, respectively (Mean = 6.28 mg (pigm) m⁻² day⁻¹; SD = 5.94 mg (pigm) m⁻² day⁻¹). Collectively, the copepods removed an average of between 31.6 % and 89.8 % of the phytoplankton standing stock per day, during April 2002 and 2004, respectively (Mean = 70.8 %; SD = 86.7 %). The daily grazing impact of the copepods accounted for an average of between 40.4 % and 87.8 % of the total zooplankton grazing impact, during April 2004 and 2005, respectively (Mean = 75.0 %; SD = 65.5 %). L. retroversa was responsible for an average of 52.4 % and 59.5 % of the total zooplankton grazing impact, during April 2002 and 2004, respectively. However, during April 2005, when L. retroversa numbers were significantly lower than previous years, the pteropod contributed an average of only 7.5 % to the total zooplankton grazing impact. Thus, during the present investigation,the pteropod was responsible for removing a mean of 48.9 % of the available phytoplankton (SD = 74.9 %). The predation impact of the dominant carnivorous macrozooplankton and micronekton in the PFZ was determined during April 2004 and 2005 using daily ration estimates obtained from the literature. Additionally, gut content analysis was used to determine the contribution of L. retroversa to the diet of the dominant predators. Average predation impact ranged from 1.1 % and 5.7 % of the total mesozooplankton standing stock during April 2004 and 2005, respectively (Mean = 3.8 %; SD = 12.3 %). Chaetognaths and euphausiids dominated total carnivore numbers and made the greatest contributions to total predation impact during both years. Copepods appeared to be the main prey item of the dominant carnivorous macrozooplankton-micronekton in the region. L. retroversa was only detected in the gut contents of the amphipod, Themisto gaudichaudi, but not in either of the chaetognath species (Eukrohnia hamata and Sagitta gazellae) or the myctophid fish (Electrona spp.). The pteropod was found in 19 % of amphipod guts dissected. Pearson’s Correlation analyses showed that the four major predatory zooplankton groups found in the PFZ (chaetognaths, euphausiids, amphipods and myctophid fish) were positively correlated to abundances of L. retroversa, suggesting that the pteropod might be an important prey item for many of the carnivorous macrozooplankton/micronekton in the PFZ. To conclude, L. retroversa may play an important role in the pelagic ecosystem of the PFZ, in austral autumn. However, ocean acidification and calcium carbonate undersaturation (as a result of increased anthropogenic carbon dioxide emissions), that is predicted to occur within the next 50 – 100 years, will most likely have significant implications for the Sub-Antarctic pelagic ecosystem if L. retroversa cannot adapt quickly enough to the changes.

The trophodynamics of the numerically dominant mesozooplankton (200-2000 m) in the vicinity of the Subtropical Convergence (STC) in the Indian sector of the Southern Ocean during austral autumn (April / May) 2007 were investigated as part of the Southern Ocean Ecosystem Variability Study. The survey consisted of six north-south transects each bisecting the STC between 38º to 43ºS and 38º to 41º45’E. In total, 48 stations situated at 30 nautical mile intervals were occupied over a period of ten days. Hydrographic data revealed a well defined surface and sub-surface expression of the STC, which appeared to meander considerably between 41ºS and 41º15’S. Surface chlorophyll-a (chla) concentrations were low, ranging between 0.08 and 0.68 mg chl-a.m-3 and were generally dominated by the picophytoplankton (<2 m) which made up 66.6% (SD±17.6) of the total pigment. Chl-a concentrations integrated over the top 150m of the water column ranged between 11.97 and 40.07 mg chl-a.m-2 and showed no significant spatial patterns (p>0.05). Total integrated mesozooplankton abundance and biomass during the study ranged between 3934.9 and 308521.4 ind.m-2 (mean = 47198.19; SD±62411.4 ind.m-2) and between 239.8 and 4614.3 mg Dwt.m-2 (mean = 1338.58; SD ±1060.5), respectively. Again, there were no significant spatial patterns in the total mesozooplankton abundance or biomass within the region of study (p>0.05). No significant correlations were found between biological (chlorophyll-a concentrations and zooplankton abundance) and physico-chemical variables (temperature and salinity) (p>0.05). The total mesozooplankton community was numerically dominated by copepods of the genera Pleuromamma, Calanus, Oncaea and Oithona. Other important representatives of the mesozooplankton community included the tunicate, Salpa thompsoni, and the pteropod, Limacina retroversa. At the 40% similarity level, numerical analysis identified five distinct mesozooplankton groupings within the survey area. Differences between the groupings were associated with changes in the relative contribution of numerically dominant species rather than the presence or absence of individual species. No groupings were associated with any specific feature of the front within the survey area. The feeding rates of the six most numerically abundant mesozooplankton species (Calanus simillimus, Limacina retroversa, Pleuromamma abdominalis, Clausocalanus breviceps, Oncaea conifera, Salpa thompsoni) accounting for on average 39% of the total mesozooplankton counts, were investigated using the gut fluorescence technique. For all species, the total gut pigment contents during the night time were significantly higher than the daytime values (p<0.05 for all species). The gut evacuation rates (k) for selected mesozooplankton ranged between 0.14 and 0.81 h-1. The ingestion rates ranged between 147.8 and 5495.4 ng(pigm)ind-1.day-1 which corresponded to a daily ration of between 2.4 and 10.9% body carbon. The combined grazing impact of the selected species on the daily phytoplankton standing stock was highly variable and ranged between 1.2 and 174.1% with an average of 27.3% (SD±38.78%) within the survey area. The highest grazing impact (>60%) was typically associated with those stations where the pteropod, L. retroversa, and the tunicate, S. thompsoni, contributed more than 5% of the total mesozooplankton counts. No significant differences were found in the grazing impact of any or all selected species situated either north, south or in the immediate vicinity of the front (p>0.05 in all cases). The lack of defined spatial patterns in the mesozooplankton abundance and community structure suggests that the STC did not act as a significant biogeographic barrier to the distribution of mesozooplankton during the study. It is presumed that the large scale mixing event caused by a storm prior to this study was responsible for the observed lack of elevated biological activity within the region of the STC.

Since the 'discovery' of the high abundance of viruses in aquatic environments, it has been generally assumed that viruses in lakes are similar to those in oceans. I directly compared these two systems using a large, robust data set. Viral abundance was significantly different among the surveyed environments. The relationship between viral and bacterial abundance indicated a fundamental difference between lakes and oceans, and suggested that viruses infecting phytoplankton may be more important in lakes. Molecular techniques (PCR & DGGE) were used to document spatial and temporal variations in the richness of viruses that infect eukaryotic phytoplankton (Phycodnaviridae) in lakes at the Experimental Lakes Area (ELA). Phycodnavirus richness was highest in the eutrophic lake, and during the spring/early summer in all the lakes. Viral richness was closely associated with phytoplankton abundance and composition. As a result, richness was influenced by trophic status, while patterns of richness were affected by regional climatic conditions. Phylogenetic analysis of environmental Phycodnavirus DNA polymerase (pol) sequences indicated that freshwater Phycodnaviruses are genetically different from cultured isolates and marine environmental sequences. A genetic distance analysis indicated that pol sequences > 7 % different infected different host species. Therefore, the 20 different freshwater sequences likely infected nine different hosts. Multivariate statistics identified seven possible phytoplankton hosts, including chlorophytes, chrysophytes, diatoms and dinoflagellates. Finally, the modified dilution experiment was evaluated as an approach for estimating viral-mediated phytoplankton mortality in two lakes at the ELA. Experiments resulted in non-significant apparent growth rate regressions. While a model analysis, indicated that the method was sensitive to poorly constrained parameters such as burst size and length of the lytic cycle, making it unsuitable for estimating mortality rates in these lakes. These studies indicate that Phycodnaviridae are a genetically rich and dynamic component of lakes. Their richness is influenced by both the chemical and physical components of their environment. Although the presence of these viruses indicates that they are a source of phytoplankton mortality, the magnitude of their impact on structuring phytoplankton communities awaits methodological advances. Nonetheless, these findings support the view that viruses infecting phytoplankton are ecologically important components of lake ecosystems. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

In agreement with global patterns of climate change and increasing temperatures in the tropical oceans, the Northern Red Sea (NRS) has been warming over the last few decades. Using 18 years of remotely-sensed chlorophyll-a data (Chl-a, an index of phytoplankton biomass), we investigate the potential impacts of climate warming on phytoplankton abundance and phenology in the Northern Red Sea by exploring the mechanistic links with the regional physical environment. The results of the analysis reveal that, in accordance with other tropical ecosystems, phytoplankton biomass in the NRS will decrease in response to warmer climate scenarios. This is attributed to lower heat fluxes (heat loss to the atmosphere) during the bloom period, and enhanced vertical stratification, which prevents vertical mixing of nutrients into the euphotic layer. In addition, we show that during warmer conditions (when heat fluxes are weakened), the winter bloom initiates significantly later (by up to 10 weeks) and its duration is considerably reduced. The biological implications of alterations to phytoplankton phenology may include increased larval mortality of pelagic species, reduced recruitment, fisheries impacts and changes to community structure.

Methods of measuring primary productivity are discussed in terms of what information they provide concerning energy flow in the phytoplankton community. A track autoradiographic technique is presented which measures species-specific phytoplankton productivity and its use is demonstrated under laboratory conditions. Controls and standardized processing conditions are established which permit the use of the track technique in quantitative evaluations of primary productivity.

No description available.