High Phytoplankton Density Research Articles

Environmental heterogeneity affecting spatial distribution of phytoplankton community structure and functional groups in a large eutrophic lake, Lake Chaohu, China

The growth and development of phytoplankton are influenced by physico-chemical parameters, which can also affect the spatial distribution of phytoplankton community structure. However, it is unclear whether environmental heterogeneity caused by multiple physico-chemical factors can affect the spatial distribution of phytoplankton and its functional groups. In this study, we investigated the seasonal variation and spatial distribution of phytoplankton community structure and its relationships with environmental factors in Lake Chaohu from August 2020 to July 2021. We recorded a total of 190 species from 8 phyla, which were divided into 30 functional groups, including 13 dominating functional groups. The average annual phytoplankton density and biomass were (5.46 ± 7.17) × 107 cells/L and 4.80 ± 4.61 mg/L, respectively. The density and biomass of phytoplankton were higher in summer ((14.64 ± 20.34) × 107 cells/L, 10.61 ± 13.16 mg/L) and autumn ((6.79 ± 3.97) × 107 cells/L, 5.57 ± 2.40 mg/L), with the M and H2 of dominant functional groups. The dominant functional groups were N, C, D, J, MP, H2, and M in spring, whereas functional groups C, N, T, and Y dominated in winter. The distribution of phytoplankton community structure and dominant functional groups exhibited significant spatial heterogeneity in the lake, which was consistent with the environmental heterogeneity of the lake and could be classified into four locations. Location I had higher phytoplankton density and biomass than the other three locations. Additionally, dominant functional groups M, C, and H2 were present throughout the lake, and all 13 dominant functional groups were observed in Location II. Our findings suggest that environmental heterogeneity is a key factor influencing the spatial distribution of phytoplankton functional groups in Lake Chaohu.

Effects of submerged macrophytes (Elodea nuttallii) on water quality and microbial communities of largemouth bass (Micropterus salmoides) ponds.

Traditional aquaculture ponds are one of the most vulnerable ecosystems; thus, ecological aquaculture is increasingly valued for its beneficial ecological properties and ecosystem services. However, little is known about ecological aquaculture of largemouth bass with submerged vegetation. Here, we designed three ecological ponds of cultured largemouth bass with submerged macrophytes (the EM group) and three ponds with traditional aquaculture (the M group) to reveal the response of water quality, and phytoplankton and bacterial communities, to submerged macrophyte bioremediation during a 90-day culture period. We observed that Cyanobacterial outbreak occurred in the M group ponds from day 7 to the end of the experiment; however, there were no Cyanobacterial blooms in the EM group ponds throughout the culture period. Compared with the M group ponds, the EM group ponds, which had submerged hydrophytes, had significantly decreased concentrations of TP, TN, and CODMn, but significantly increased DO concentrations throughout the experimental period. Moreover, ecological aquaculture with submerged macrophytes showed strong effects on the phytoplankton and bacterial community compositions. In particular, the M group ponds had higher phytoplankton density and mainly included Cyanobacteria, whereas the EM group had lower phytoplankton density and mainly included Chlorophyta. Moreover, higher alpha diversity, as determined by Ace and Simpson index values, was detected for bacterial communities in the EM group ponds. Furthermore, PCoA clearly grouped the bacterial communities according to the two culture modes throughout the culture period. These results indicate that ecological aquaculture with submerged macrophytes can improve water quality, control Cyanobacterial blooms, and affect the diversity and composition of bacterial communities. These valuable effects seem to be beneficial and consistent to maintaining aquaculture ecosystem stability.

Seasonal changes in phytoplankton assemblages and environmental variables in highly turbid tropical estuaries of the Mekong River, Vietnam.

The distribution of phytoplankton assemblages in response to physicochemical variables was assessed using Spearman's correlation and canonical correspondence analysis in four highly turbid estuaries of the Mekong River (MKR) system in Ben Tre Province, Vietnam. During two surveys (September 2017 and April 2018) at 20 sampling sites, a total of 162 species were recorded, with a dominance of diatoms (> 50%). Phytoplankton abundance varied from 3.01 × 105 to 11.85 × 105 cells/L, with the highest cell densities found at the BL2 station in the rainy season, mainly attributed to cyanobacteria during the rainy period, whereas diatoms were dominant in the dry season. Chlorophyll-a concentration in this area was low and decreased from the mouth stations. Similarity analysis distinguished the freshwater and oligohaline regions (characterized by lower phytoplankton abundance in the oligohaline areas) from the mesohaline and polyhaline zones (characterized by higher phytoplankton density in the polyhaline sections), based on the salinity gradient, which mostly explained the spatio-temporal distribution of phytoplankton. In which, freshwater and oligohaline sites were dominated by the diatom Coscinodiscus, the euglenoids Lepocinclis, and the green alga Scenedesmus in the rainy season, while mesohaline and polyhaline stations were dominated only by diatom species (Thalassionema and Skeletonema) in the dry season. High salinity and total dissolved solutes, and low nutrients are the major factors affecting phytoplankton growth and lead to low density and low primary biomass in turbid estuarine systems like the MKR estuaries. Our results further emphasize the importance of taking into account of salinity in understanding seasonal changes of phytoplankton communities, which can provide a valuable baseline data for ecological management strategies in tropical estuarine ecosystems.

Assessing growth performance and survival of wild shad Tenualosa ilisha fry in two earthen ponds with different feeding regime: A new insight for conservation

The present study describes the rearing and growth performance of Hilsa (Tenualosa ilisha) fry in experimental trial performed in earthen pond ecosystem located adjacent to river Rupnarayan for developing in-situ rearing protocol of fry collected from the wild sources. The seed was collected during May, 2020 from the river and stocked in two different rearing ponds. One of the ponds was provided with artificial feed and another fed with chicken offal to raise the production of zooplankton. Routine monitoring of water and soil quality parameters as well as other biotic communities like plankton was performed to understand the dynamics of ecological conditions in relation to changes in length and weight. The results of PCA between sediment quality and specific growth of fish indicated the strong positive loading of available nitrogen, available phosphate and free calcium carbonate, while moderate positive loading was observed with percentage of silt. Interestingly, it is observed that survivability rate of fish was approximately 80% in both the ponds. The results indicated natural growth fish was considerably well in both the experimental ponds. However, higher growth of juveniles were observed in the pond 2 with higher phytoplankton density (9120cells/L) than pond 1 having lower phytoplankton density (920cells/L) at the end of the experiments. The water quality parameters were comparable in both the experimental ponds. Based on this study it is evident that plankton (especially zooplankton) has induced better growth in pond 2 and possible incorporation of live feed along with formulated feed might trigger better growth of the stocked Hilsa. The present study provides new insight in developing field based approaches for successful rearing and conservation of threatened Hilsa in Indian waters.

Influence of environmental factors on biology and catch composition of Barbonymus schwanenfeldii in a tropical lake, northern Malaysia: implications for conservation planning.

Very little work has determined the relative importance of uncontrolled environmental factors for affecting fish biology, and how these might influence gillnet catches. This study addresses this deficit for an important Southeast Asian cyprinid (Barbonymus schwanenfeldii). Fish were caught monthly for 12 months using gillnets of three different mesh sizes, each of which was deployed in duplicate at the surface of one of three randomly selected sites in Lake Kenyir, Malaysia, concurrent with determining various environmental parameters and the abundance of phytoplankton (chlorophyll-a). Results indicated that growth co-efficient of B. schwanenfeldii was positively influenced by dissolved oxygen and negatively influenced by total inorganic nitrogen, whereas an opposite result was observed in case of the hepatosomatic index of fish. Water turbidity was a limiting factor only for small fish (mean total length: 15.74±1.10 cm). B. schwanenfeldii could best be caught during the period of high phytoplankton abundance or at the location of high phytoplankton density in the water. Water temperature negatively influenced the gillnet catches of the fish. The remaining environmental factors such as water depth, pH, and phosphate had a weak and insignificant influence (P >0.05) on the biology and gillnet catches of fish. The observed results can be very useful for the ecological monitoring and conservation plans for this species in relation to climate change. Furthermore, the utility of the similar data for other species would be useful not only forregional but also forinternational fishery by optimizing catches considering environmental conditions.

Distribution of phytoplankton in Pangkep Waters, South Sulawesi, Indonesia

The coastal water of Pangkajene Kepulauan, or Pangkep, in South Sulawesi has been influenced by high anthropogenic activities, where the inflow of nutrient from the land has caused several cases of harmful algal blooms and mass fish mortality. Thus, it was important to understand the community structure and distribution of phytoplankton, with particular interest on the bloom-forming and harmful genus, to better mitigate the effects of harmful algal blooms in the future. Sample collection for this study was conducted on May 2017 at 22 stations from three zones, the northern, middle, and southern coastal area of Pangkep. From this study, the phytoplankton density in Pangkep was found varied between 2.179 × 106 cells/m3 to 2.192 × 108 cells/m3, with the highest density of phytoplankton was observed in the northern and southern area of Pangkep. On the other hand, the middle area has lower phytoplankton density but has the highest diversity and evenness. Two stations, station 15 and 21, have a distinct phytoplankton community structure which might have caused by a combined effect of temperature and nutrient input from the land. Twenty-nine genera of phytoplankton were observed, with the diatoms Skeletonema as the most dominant genus which contributes to over 95% of total phytoplankton density. The occurrence of Ceratium, which once was found as a dominant genus in Pangkep coastal and estuaries, has caused a concern whether it might blooms and replacing the dominance of diatoms in these areas.

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

Baltic coastal lagoons are severely threatened by eutrophication. To evaluate the impact of eutrophication on macrophytobenthos, we compared the seasonal development in macrophytobenthic composition, biomass and production, water column parameters (light, nutrients), phytoplankton biomass and production in one mesotrophic and one eutrophic German coastal lagoon. We hypothesized that light availability is the main driver for primary production, and that net primary production is lower at a higher eutrophication level. In the mesotrophic lagoon, macrophytobenthic biomass was much higher with distinct seasonal succession in species composition. Filamentous algae dominated in spring and late summer and probably caused reduced macrophytobenthic biomass and growth during early summer, thus decreasing vegetation stability. Light attenuation was far higher in the eutrophic lagoon, due to high phytoplankton densities, explaining the low macrophytobenthic biomass and species diversity in every season. Areal net primary production was far lower in the eutrophic lagoon. The “paradox of enrichment” hypothesis predicts lower production at higher trophic levels with increased nutrient concentrations. Our results prove for the first time that this hypothesis may be valid already at the primary producer level in coastal lagoons.

Phycolimnological study of some wastewater of Sulaimani Provience -Kurdistan Region of Iraq

This work is aimed to study the characteristics of some wastewater in Sulaimani city. Water samples were collected monthly from October 2018 to May 2019 from four sites, two of them Site1:Tanjaro River before bridge,Site 2:Tanjaro River after bridge along Tanjaro river , Site3:kana swra and Site4:Awbara from weast water of Sulaimani city box channels which finally flow into Tanjaro river . To represent their water quality some physical , chemical and Biological analysis were conducted. The mean value of pH for all studied sites was found to be above 7 . The value of Electrical conductivity(EC) in Sites 1,2,3 and 4 were ranged between(407-601 µs/cm),( 266-585 µs/cm) ,( 773-1004 µs/cm) and(398-975 µs/cm)respectively, Turbidity ranged between(42-1001 NTU),( 57-986 NTU),( 32-1010.5 NTU) and(41-643 NTU) in Site 1,2,3 and 4 respectivly and Chemical Oxygen Demand (COD) value in Site 1,2,3 and 4 were ranged between(251-975.5 mg/L),( 275-926 mg/L),( 354-1025 mg/L) and(452-1025 mg/L) respectively. A total of 114 algal taxa were identified belonging to 7 classes, 63 taxa belonged to Bacillariophyceae species, they were the most abundant group (4 taxa belong to centrales and 59 taxa belonging to pinnales), followed by 24 taxa of Cyanophyceae ,22 taxa chlorophyceae, , 2 taxa Pyrophyceae and 1 taxa for each of Euglenophyceae, Rhodophyceae and Xanthophyceae. Higher phytoplankton density was recorded in Awbara (58269.44ind×103/L), while the lowest density was recorded in Tanjaro River after the bridge which was (14300.2ind×103/L).

Response of phytoplankton assemblages to variations in environmental parameters in a subtropical bay (Chabahar Bay, Iran): Harmful algal blooms and coastal hypoxia

The present work is a comprehensive study on the spatiotemporal variation of environmental parameters in relation to phytoplankton assemblages over a one-year period (March 2017–March 2018) at a semi-enclosed subtropical bay and adjacent coastal waters in the north of Gulf of Oman. The physical and biological parameters were mostly controlled by the southwest monsoon which usually lasts 4 months (June–September) in the region. The outstanding phenomena which highly affected the physicochemical parameters and biological activity were thermal stratification (established in the May–October period), and rising concentration of nutrients due to monsoon-driven upwelling in the late monsoon and post-monsoon periods. As a consequence, the hypoxic condition was established and the pH was also decreased to values smaller than 8.0. It seems that the nitrate concentration limits phytoplankton growth during most times of the year. However, the results showed that the phytoplankton population in the fall inter-monsoon period may also be controlled by silicate availability as its concentration declined to values as small as 0.8 μM in January. Chlorophyll a concentration showed a strong peak in January and a weaker peak in October. The former is due to the intense blooms of Noctiluca scintillans and the later was coincided with high nutrient concentrations and high phytoplankton density and diversity. Diatoms (93%) were dominant during the course of sampling and dinoflagellates (4.5%) were second in dominance. Exceptions were observed in March 2017 when the outbreak of dinoflagellates led to extensive water discoloration and in April 2017 during the massive bloom of Mesodinium rubrum. The most abundant genera were diatoms Pseudo-nitzschia (34.8%), Nitzschia (23.9%), Hemiaulus (20%), and Leptocylindrus (6.1%). While dinoflagellates blooms mostly occurred during high nutrients concentrations in late SW monsoon and inter-monsoon seasons; the bloom of potentially harmful diatoms occurred during the SW monsoon season.

Spatial, seasonal variation and biodiversity in phytoplankton communities in Al-Diwaniyah River -IRAQ

Identification and diversity of Phytoplanktons was studied in five sites in the River of Al-Diwaniyah – Iraq during the period from January 2018 to December 2018. A total of 224 taxa belonging to 66 genera were diagnosed in all study sites. Atotal of 224 taxa were identified in all stations of study and dominated by diatoms (120 taxa).pennales were represented by 107 species only, and 13 species belong to Centrales diatoms followed by green algae recorded 54 species and then blue green 42 species. Euglenophyta recorded 6 species, while the Pyrrophyceae was one species. It was also notice that few genera were dominated namely, Oscilltoria spp., Scendesmes spp., Cocconies placentula, Cyclotella meneghiniana, Melosira ambigua, Navicula cincta, Synedra acus, during the period of the study in all stites.. The highest density of phytoplankton was recorded during the month of April, at 2918.4 × 310 cells / liter, and the lowest density at site (3) during the month of January was 278.3 × 310 cells / liter. Shannon -Weiner for Diversity showed the highest value in Site (1) at 3.66 during April and the lowest value on site (3) in February and reached 1.19.

Revisiting the role of top-down and bottom-up controls in stabilisation of nutrient-rich plankton communities

Understanding the conditions for successful control of phytoplankton by zooplankton in eutrophic ecosystems is a highly important research area with a wide implementation of mathematical modelling. Theoretical models generally predict destabilisation of food webs in eutrophic environments with large-amplitude oscillations of population densities which would eventually result in species extinction. On the other hand, these theoretical predictions are often at odds with ecological observations demonstrating stable dynamics even for a high nutrient load. This apparent discrepancy is known in the literature as Rosenzweig's “paradox of enrichment”. Recent theoretical works emphasize a crucial role of spatial heterogeneity in successful top-down control in eutrophic environment; however, the interplay between the top-down and bottom-up mechanisms as well as the role of animal movement in system stabilisation are still unclear. Here we extend previous theoretical studies on plankton interactions by considering the important scenario where main consumers of phytoplankton are mesozooplankton (large grazers) with a slow reproduction timescale compared to their fast movement across the column. By exploring a system of integro-differential equations, we find that stabilisation of plankton dynamics in nutrient-rich waters occurs even when the functional response of grazers shows a pronounced saturation, which is impossible for a well-mixed system. Unlike previous findings, we show that accumulation and feeding of zooplankton at depths with higher phytoplankton density can be a destabilising factor. We find that the interplay between the two different types of light attenuation in the water – the algal self-shading and water adsorption - can result in high amplitude oscillations of plankton densities, whereas each mechanism alone acts as a stabilising factor.

Presence and Composition of Planktons’ Organisms in Ships Ballast Water Discharged in Al-Mukalla Harbor, Gulf of Aden

This was the first study in Yemen, and Gulf of Aden aims to investigate the marine organisms in ballast water and sediments, and gives baseline information defines the zooplankton, phytoplankton and invertebrates, associated fuel tankers. Samples from Ballast water were taken from three ships that arrived at Mukalla Port, the Hadhramout coast from ports of Hamriyah port, U.A.E; ports of Taheri, Iran; and Bosaso Somalia (MT: Gulf Petroleum III, MT: Prime Royal, and M T: Breu) respectively. The marine organisms in samples were presented by three taxonomic groups, phytoplankton, zooplankton and benthos. Fifty-eight taxa were identified within this study; which consisted of 17 phytoplankton, 18 zooplanktons and 23 Benthos. The highest density of phytoplankton was 21 Ind/L, with the occurrence of 17 species found in ballast water, while 22 Ind/50cc of 2 species in sediment samples of the tanker Beru, and fewer densities were in Gulf Petroleum and Prim Royal. The most common phytoplankton observed were Coscinodiscus granii, Coscinodiscus jonesianus and Thalassiosira eccentric. The low Zooplankton density was 13 Ind/L with an occurrence of 18 species found in Prim Royal tanker. Copepods were the most dominant zooplankton among the three tankers. Paracalanus parvus had the highest value of dominance followed by Calanopia parathompsoni, Acrocalanus gracilis and Paracalanus denudatus had the lowest occurrence over three tankers. Seven taxa of Dinoflagellates were identified; two of them Ceratium fusus and polykrikos sp. are known to be harmful species.

Phytoplankton abundance in relation to the quality of the coastal water – Arabian Gulf, Saudi Arabia

Phytoplankton abundance in relation to some physicochemical characters of the costal water of Arabian Gulf (Saudi Arabia) was studied for one year. The sampling program included 15 locations in Dammam, Saihat, Al-Qatif, Al-Awamia and Safwa. Water samples were analyzed monthly for these parameters; temperature, pH, salinity, dissolved oxygen, nitrite, nitrate, ammonia, carbon dioxide, total chloride, reactive orthophosphate and total phosphorus and alkalinity, also phytoplankton communities were identified and Chlorophyll a was estimated. The results showed that, the high phytoplankton density attaining the maximum (190.3 × 104/m3) during May and June, and the minimum (10.4 × 104/m3) during November and December. Forty Five species belonging to 5 phytoplankton groups were recorded. Bacillariophyceae was the first dominant group forming 48% of the total phytoplankton communities (23 species). The dominant species of Bacillariophyceae were Pleurosigma strigosum, Pleurosigma elongatum, Lyrella clavata, Rhizosolenia shrubsolei, Cylindrotheca closterium, Nitzschia panduriform, Nitzschia longissimia, Amphora sp and Stephanopyxis. Dinophyceae was the second dominant group and formed 31% of the total phytoplankton communities (10 species); the dominant species were Ceratium fusus, Heterosigma sp, Ceratium furca, Prorocentrum triestium, Protoperidinium sp, Gyrodinium spirale, Noctiluca scintillans and Scrippsiella trochoidea. Cyanophyceae formed 13% (5 species) where Nostoc sp, Oscillatoria and Merismopedia sp were the dominant species. Chlorophyceae had 8% (6 species); Scendesmus sp., Chlorella sp., Chlamydomonas sp., Dunaliella salina and Nannochloropsis sp were the dominant species. The Euglinophyceae was rare only one species (Euglina sp). The relationship was positive between the phytoplankton, chlorophyll a and carbon dioxide while negative amongst dissolved oxygen and total nitrogen. This research indicated that the relation between water quality and phytoplankton organisms at the coast of Arabian Gulf (Saudi Arabia) was extremely overlapping and interdependent; any changes in the one component may significantly affect those of the other components.

Increasing phytoplankton-available phosphorus and inhibition of macrophyte on phytoplankton bloom.

We assembled mesocosms to address the coherent mechanisms that an increasing phosphorus (P) concentration in water columns coupled with the phytoplankton bloom and identify the performance gap of regulating phytoplankton growth between two macrophyte species, Ceratophyllum demersum L. and Vallisneria spiralis L. Intense alkaline phosphatase activities (APA) were observed in the unplanted control, with their predominant part, phytoplankton APA (accounting for up to 44.7% of the total APA), and another large share, bacterial APA. These correspond with the large average concentration of total phosphorus (TP), total dissolved phosphorus (TDP) and soluble reactive (SRP) as well as high phytoplankton density in the water column. The consistency among P concentrations, phytoplankton density and APA, together with the positive impact of phytoplankton density on total APA revealed by the structural equation modelling (SEM), indicates that facilitated APA levels in water is an essential strategy for phytoplankton to enhance the available P. Furthermore, a positive interaction between phytoplankton APA and bacteria APA was detected, suggesting a potential collaboration between phytoplankton and bacteria to boost available P content in the water column. Both macrophyte species had a prominent performance on regulating phytoplankton proliferation. The phytoplankton density and quantum yield in C. demersum systems were all significantly lower (33.8% and 24.0%) than those in V. spiralis systems. Additionally, a greater decoupling effect of C. demersum on the relationship between P, APA, phytoplankton density, bacteria dynamic and quantum yield was revealed by SEM. These results imply that the preferred tactic of different species could lead to the performance gap.

Some Limiting Factors in Superintensive Production of Juvenile Pacific White Shrimp, Litopenaeus vannamei, in No‐water‐exchange, Biofloc‐dominated Systems

AbstractSuperintensive shrimp culture in zero‐exchange, biofloc‐dominated production systems is more biosecure and sustainable than traditional shrimp farming practices. However, successful application of this technology depends upon optimizing dietary formulations, controlling Vibrio outbreaks, and managing accumulative changes in water quality and composition. A 49‐d study investigated the effect of two commercial feeds of differing protein content and an indoor limited‐exchange, biofloc‐dominated culture environment on Litopenaeus vannamei performance and tissue composition, water quality and ionic composition, and Vibrio dynamics. Juveniles (5.3 g) were stocked at 457/m3 into four 40 m3 shallow raceways containing biofloc‐dominated water and fed one of two commercial feeds with differing protein content, 35 or 40%. Shrimp performance, Vibrio populations, and changes in shrimp and culture water composition were monitored. There were no significant differences (P > 0.05) in shrimp performance (survival, weight, growth, specific growth rate, total biomass, yield, feed conversion ratio, and protein efficiency ratio) or proximate composition between feed types. The 40% protein feed resulted in higher culture water nitrate and phosphate concentrations, alkalinity consumption and bicarbonate use, and higher phytoplankton density. The presence of Vibrio, specifically Vibrio parahaemolyticus, reduced shrimp survival. This survival decrease corresponded with increased culture water Vibrio concentrations. Culture water K+ and Mg2+ increased significantly (P < 0.05), and Sr2+, Br−, and Cl− decreased significantly (P < 0.05) over time. While Cu2+ and Zn2+ did increase in shrimp tissue, no heavy metals accumulated to problematic levels in culture water or shrimp tissue. These results demonstrate the importance of monitoring Vibrio populations and ionic composition in limited‐exchange shrimp culture systems.

Oil spill dispersants induce formation of marine snow by phytoplankton-associated bacteria

Unusually large amounts of marine snow, including Extracellular Polymeric Substances (EPS), were formed during the 2010 Deepwater Horizon oil spill. The marine snow settled with oil and clay minerals as an oily sludge layer on the deep sea floor. This study tested the hypothesis that the unprecedented amount of chemical dispersants applied during high phytoplankton densities in the Gulf of Mexico induced high EPS formation. Two marine phytoplankton species (Dunaliella tertiolecta and Phaeodactylum tricornutum) produced EPS within days when exposed to the dispersant Corexit 9500. Phytoplankton-associated bacteria were shown to be responsible for the formation. The EPS consisted of proteins and to lesser extent polysaccharides. This study reveals an unexpected consequence of the presence of phytoplankton. This emphasizes the need to test the action of dispersants under realistic field conditions, which may seriously alter the fate of oil in the environment via increased marine snow formation.

DINÁMICA DEL FITOPLANCTON DE LA CIÉNAGA GRANDE DE SANTA MARTA, CARIBE COLOMBIANO

In order to assess phytoplankton dynamics in the Ciénaga Grande de Santa Marta, bimonthly sampling was done at six stations from March 1996 to February 1997. Salinity showed wide ranges so the year could be divided in four seasons. Higher salinities were related to higher phytoplankton density, while lower salinities were related to lower phytoplankton densities and increased species richness. 224 taxa were recorded, and the general trend was towards a low diversity with a few dominant species, and most of them rare. Cyanophytes showed the highest abundances all year. Salinity, turbidity and orthophosphates were the environmental factors best related to the biotic data. Seasonal changes in phytoplankton concerning to meteorological conditions, fresh and tidal floods and dredging of Clarín canal are discussed.

Quantification of phytoplankton bloom dynamics by citizen scientists in urban and peri-urban environments.

Freshwater ecosystems are severely threatened by urban development and agricultural intensification. Increased occurrence of algal blooms is a main issue, and the identification of local dynamics and drivers is hampered by a lack of field data. In this study, data from 13 cities (250 water bodies) were used to examine the capacity of trained community members to assess elevated phytoplankton densities in urban and peri-urban freshwater ecosystems. Coincident nutrient concentrations and land use observations were used to examine possible drivers of algal blooms. Measurements made by participants showed a good relationship to standard laboratory measurements of phytoplankton density, in particular in pond and lake ecosystems. Links between high phytoplankton density and nutrients (mainly phosphate) were observed. Microscale observations of pollution sources and catchment scale estimates of land cover both influenced the occurrence of algal blooms. The acquisition of environmental data by committed and trained community members represents a major opportunity to support agency monitoring programmes and to complement field campaigns in the study of catchment dynamics.Electronic supplementary materialThe online version of this article (doi:10.1007/s10661-015-4912-9) contains supplementary material, which is available to authorized users.

A preliminary study on limnological stock assessment, productivity and potential fish yield of Omi Dam, Nigeria

This study examined the water quality, primary productivity, plankton and the potential fish yield of Omi dam for management purposes. Among the physico-chemical parameters analyzed, Ca2+ and HCO3, were found to be above permissible limits ((3.90 ± 0.68, 24.50 ± 7.33, respectively). A total of 24 species of phytoplankton belonging to three major taxa were recorded. Most species were of the class chlorophyta, followed by chrysophyta then cyanophyta. The highest density of phytoplankton was in January (740 No. ml-1), while the lowest (300 No. ml-1) was recorded in April all in station 3. The mean density recorded for each month was 555, 333 and 410 No. ml-1 for January, April and June respectively. A total of 23 zooplankton species was recorded predominated by rotifera, followed by cladocerans and copepod respectively. Density was highest (5.00 ind.L-1) in station 1 in April, while it was lowest (0.32 ind.l-1) in station 2 in June. Mean density for each month was 0.92, 2.95 and 0.57 (ind.L-1) for January, April and June respectively for the three stations sampled. Sorenson’s index of similarity for zooplankton species between the months showed that there was similarity throughout the period of the study. There was also similarity in the phytoplankton except between the months of January and June. Mean gross pelagic primary productivity (GPP) was high (19.58 g O2 m-2d-1) when compared to other water bodies. Mean potential fish yield (PFY) of 34.77 kg ha-1 was calculated based on the morpho edaphic index (MEI). Observations are discussed and recommendations are made. Key words: Physico-chemical, assessment, phytoplankton, zooplankton, Sorenson

Air–sea CO 2 exchange of beach and near-coastal waters of the Chukchi Sea near Barrow, Alaska

Partial pressure of CO 2 in equilibrium with sample water (pCO 2) for the coastal water in the Chukchi Sea was continuously observed in summer, 2008. Average daily CO 2 flux calculated from the pCO 2 and gas transfer coefficients ranged from −0.144 to −0.0701 g C m −2 day −1 depending on which gas transfer coefficient was used. The pCO 2 before the landfast ice sheets melted appeared to be highly biologically controlled based on the following information: (1) the diurnal pattern of pCO 2 was strongly correlated with Photosynthetic Photon Flux Density (PPFD); (2) high chlorophyll density was observed during periods of peak uptake; and (3) the day-to-day variation in the pCO 2 strongly correlated with the presence or absence of near-shore ice sheets. The lowest pCO 2 of 35 ppm together with the highest PPFD of 1362 μmol E m −2 s −1 were observed in the afternoon on June 28 in the presence of sea ice. The very low pCO 2 observed in late June was likely caused by high photosynthetic rates related to high phytoplankton densities typically observed from spring to early summer near the ice edge, and by water low in salinity and CO 2 released by melting sea ice early in the season.