Increases in Picocyanobacteria Abundance in Agriculturally Eutrophic Pampean Lakes Inferred from Historical Records of Secchi Depth and Chlorophyll-a

Phytoplankton size structure has profound consequences on food-web organization and energy transfer. Presently, picocyanobacteria (size < 2 µm) represent a major fraction of the autotrophic plankton of Pampean lakes. Glyphosate is known to stimulate the development of picocyanobacteria capable of degrading the herbicide. Due to the worldwide adoption of glyphosate-resistant crops, herbicide usage has increased sharply since the mid-1990s. Unfortunately, there are very few studies (none for the Pampa region) reporting picocyanobacteria abundance before 2000. The proliferation of µm sized particles should decrease Secchi disc depth (ZSD). Therefore ZSD, conditional to chlorophyll-a, may serve as an indicator of picocyanobacteria abundance. We use generalized additive models (GAMs) to analyze a “validation” dataset consisting of 82 records of ZSD, chlorophyll-a, and picocyanobacteria abundance from two Pampean lakes surveys (2009 and 2015). In support of the hypothesis, ZSD was negatively related to picocyanobacteria after accounting for the effect of chlorophyll-a. We then fitted a “historical” dataset using hierarchical GAMs to compare ZSD conditional to chlorophyll-a, before and after 2000. We estimated that ZSD levels during 2000–2021 were, on average, only about half as deep as those during 1980–1999. We conclude that the adoption of glyphosate-resistant crops has stimulated outbreaks of picocyanobacteria populations, resulting in lower water transparency.

Studies on New Zealand Bivalve Larvae, with Observations on the Adults, and on the Hydrology of Bay of Islands and Wellington Harbour

<p>1) Observations made on some hydrological parameters at Bay of Islands and Wellington Harbour during 1970-71 are presented and discussed. The parameters include water temperature, salinity, dissolved oxygen content and turbidity. The water current system in Bay of Islands is also discussed and a proposed pattern presented. The hydrology of Bay of Islands and Wellington Harbour are compared. Bay of Islands is topographically lees isolated from oceanic influence than Wellington Harbour, and there is a more marked change from estuarine to oceanic hydrological conditions within the bay. Monthly mean surface seawater tempe ratures at Bay of Islands exceed those of Wellington Harbour by about 4 degrees C. Water temperature stratification is more marked in Bay of Islands than Wellington Harbour, suggesting less efficient water mixing. Salinities are lower in Wellington harbour (normally about 33.5 - 34.5 parts per thousand) than the main basin of Bay of Islands (normally about 3S.5. parts per thousand). Turbidities in estuarine areas of Bay of Islands are similar to those for most of Wellington Harbour ( 3 - 6 metres Secchi Disc visibility values), but are much Less in outer basin areas (Secchi Disc visibility values may exceed 15 metres). Dissolved oxygen content is high in both harbours, frequently exceeding 100 per cent saturation in surface water. The results suggest that although both harbours are hydrologically quite homogeneous, Wellington Harbour is more efficiently mixed than Bay of Islands. (2) Benthic and shore collections of marine bivalve molluscs were made in Bay of Islands, and benthic collections were made in Wellington Harbour, during 1970-72. The species occurring are recorded and discussed, and the distribution of some common species in Wellington Harbour is related to sediment types. A list of bivalve molluscs collected in Bay of Islands is presented, and additional species to previous Wellington Harbour species lists are recorded. Invertebrate marine communities described for New Zealand are discussed, and the bivalve fauna of both harbours is visually compared to these communities. The observations at fifty four anchor dredge benthic stations in Wellington Harbour are then treated statistically, and compared to the visual assessments. It appears that the great variability in Wellington Harbour sediments makes identity of classical communities in the harbour almost impossible. However, station groups (groups of stations with similar bivalve species present) are evident, and their distribution in Wellington Harbour correlate closely to sediment type distribution. Lists of the most abundant bivalve species occurring in both harbours, deduced from all the observations presented in this study, are given. (3) Observations were made on the occurrence of common late stage bivalve larvae in the plankton at Bay of Islands and Wellington Harbour during 1979 - 71. Three stations in Bay of Islands and four stations in Wellington Harbour were sampled approximately monthly. The bivalve larvae in shorter series of plankton samples from Raumati Beach, Dargaville Beach, Mahurangi, Ohiwa Harbour, Raglan Harbour and Kaipara Harbour during 1971 - 72 were also analysed. Twenty-nine species of bivalve larvae from these plankton samples are described. Twenty-three species of late stage bivalve larvae are provisionally identified, the identifications being based on the larval hinge structure, the distribution and abundance of the larvae in relation to adult stocks, and in some cases by correlation with the adult gonad or condition index cycle. The broad seasonal pattern of occurrence of twenty five species of late stage bivalve larvae in the plankton at Bay of Islands, Wellington Harbour and Raumati Beach is presented. (4) Ecological studies made on bivalve larvae at Bay of Islands and Wellington Harbour during 1970 - 71, are presented and compared to other published studies from overseas. Included are observations on the vertical meso-distribution of bivalve larvae over tidal cycles in estuarine and non-estuarine localities of l2m to l5m depth, the daytime vertical meso-distribution of bivalve larvae in non-estuarine water 20m- 30m in depth, the effect of light on the vertical meso-distribution of bivalve larvae in water 15m- 30min depth, and the horizontal mega-distribution of bivalve larvae in Wellington Harbour and Bay of Islands. The observations suggest that in estuarine areas, the effect of alternating tides on the vertical distribution of bivalve larvae far outweighs the effects of any other factors. During the flood tide, bivalve larvae rise from the bottom into the water column and are carried up the estuary by the tide. During the ebb tide the larvae settle and remain on the bottom. In non-estuarine areas, no such vertical migration was observed. Gravity, light and water currents, in particular, affect the vertical distribution of bivalve larvae in these areas. The horizontal mega-distribution of bivalve larvae within Wellington Harbour is fairly uniform. In Bay of Islands, bivalve larvae occur in greatest densities near the shores, while much of the central basin is almost devoid of larvae. This distribution is due to the proximity of the adult stocks to the regions of most larvae, and to the prevailing water current pattern within the bay.</p>

Studies on New Zealand Bivalve Larvae, with Observations on the Adults, and on the Hydrology of Bay of Islands and Wellington Harbour

<p>1) Observations made on some hydrological parameters at Bay of Islands and Wellington Harbour during 1970-71 are presented and discussed. The parameters include water temperature, salinity, dissolved oxygen content and turbidity. The water current system in Bay of Islands is also discussed and a proposed pattern presented. The hydrology of Bay of Islands and Wellington Harbour are compared. Bay of Islands is topographically lees isolated from oceanic influence than Wellington Harbour, and there is a more marked change from estuarine to oceanic hydrological conditions within the bay. Monthly mean surface seawater tempe ratures at Bay of Islands exceed those of Wellington Harbour by about 4 degrees C. Water temperature stratification is more marked in Bay of Islands than Wellington Harbour, suggesting less efficient water mixing. Salinities are lower in Wellington harbour (normally about 33.5 - 34.5 parts per thousand) than the main basin of Bay of Islands (normally about 3S.5. parts per thousand). Turbidities in estuarine areas of Bay of Islands are similar to those for most of Wellington Harbour ( 3 - 6 metres Secchi Disc visibility values), but are much Less in outer basin areas (Secchi Disc visibility values may exceed 15 metres). Dissolved oxygen content is high in both harbours, frequently exceeding 100 per cent saturation in surface water. The results suggest that although both harbours are hydrologically quite homogeneous, Wellington Harbour is more efficiently mixed than Bay of Islands. (2) Benthic and shore collections of marine bivalve molluscs were made in Bay of Islands, and benthic collections were made in Wellington Harbour, during 1970-72. The species occurring are recorded and discussed, and the distribution of some common species in Wellington Harbour is related to sediment types. A list of bivalve molluscs collected in Bay of Islands is presented, and additional species to previous Wellington Harbour species lists are recorded. Invertebrate marine communities described for New Zealand are discussed, and the bivalve fauna of both harbours is visually compared to these communities. The observations at fifty four anchor dredge benthic stations in Wellington Harbour are then treated statistically, and compared to the visual assessments. It appears that the great variability in Wellington Harbour sediments makes identity of classical communities in the harbour almost impossible. However, station groups (groups of stations with similar bivalve species present) are evident, and their distribution in Wellington Harbour correlate closely to sediment type distribution. Lists of the most abundant bivalve species occurring in both harbours, deduced from all the observations presented in this study, are given. (3) Observations were made on the occurrence of common late stage bivalve larvae in the plankton at Bay of Islands and Wellington Harbour during 1979 - 71. Three stations in Bay of Islands and four stations in Wellington Harbour were sampled approximately monthly. The bivalve larvae in shorter series of plankton samples from Raumati Beach, Dargaville Beach, Mahurangi, Ohiwa Harbour, Raglan Harbour and Kaipara Harbour during 1971 - 72 were also analysed. Twenty-nine species of bivalve larvae from these plankton samples are described. Twenty-three species of late stage bivalve larvae are provisionally identified, the identifications being based on the larval hinge structure, the distribution and abundance of the larvae in relation to adult stocks, and in some cases by correlation with the adult gonad or condition index cycle. The broad seasonal pattern of occurrence of twenty five species of late stage bivalve larvae in the plankton at Bay of Islands, Wellington Harbour and Raumati Beach is presented. (4) Ecological studies made on bivalve larvae at Bay of Islands and Wellington Harbour during 1970 - 71, are presented and compared to other published studies from overseas. Included are observations on the vertical meso-distribution of bivalve larvae over tidal cycles in estuarine and non-estuarine localities of l2m to l5m depth, the daytime vertical meso-distribution of bivalve larvae in non-estuarine water 20m- 30m in depth, the effect of light on the vertical meso-distribution of bivalve larvae in water 15m- 30min depth, and the horizontal mega-distribution of bivalve larvae in Wellington Harbour and Bay of Islands. The observations suggest that in estuarine areas, the effect of alternating tides on the vertical distribution of bivalve larvae far outweighs the effects of any other factors. During the flood tide, bivalve larvae rise from the bottom into the water column and are carried up the estuary by the tide. During the ebb tide the larvae settle and remain on the bottom. In non-estuarine areas, no such vertical migration was observed. Gravity, light and water currents, in particular, affect the vertical distribution of bivalve larvae in these areas. The horizontal mega-distribution of bivalve larvae within Wellington Harbour is fairly uniform. In Bay of Islands, bivalve larvae occur in greatest densities near the shores, while much of the central basin is almost devoid of larvae. This distribution is due to the proximity of the adult stocks to the regions of most larvae, and to the prevailing water current pattern within the bay.</p>

Analisis Kesesuaian Kawasan Perairan untuk Ekowisata Diving di Pulau Soreh Kabupaten Bintan

Tujuan penelitian ini adalah untuk mengetahui potensi ekologis serta analisis kesesuaian dan daya dukung kawasan perairan Pulau Soreh untuk ekowisata diving. Metode penelitian yang digunakan adalah metode survei dengan teknik pengambilan sampel secara purposive sampling yang terdiri dari 2 stasiun. Pengambilan data karang mengunakan metode PIT (Point Intersept Transect), data ikan menggunakan metode UVC (Underwater Visual Census), data kecerahan mengggunakan secchi disc, data kecepatan arus menggunakan botol berisi air dan dikat dengan tali berukuran yang sudah ditentukan, data kedalaman menggunakan bandul atau pemberat dengan tali yang sudah ditentukan ukurannya dan data sosial dengan metode wawancara. Berdasarkan hasil pengamatan potensi tutupan karang hidup sebesar 1–70 %, kecerahan perairan memiliki kecerahan berkisar 47,2-100%, jumlah jenis life form karang sebanyak 1-13 jenis, jenis ikan karang sekitar 4-14 jenis, kecepatan arus sebesar 10,82-13,36 cm/detik, kedalaman terumbu karang sekitar 3,50-10 meter, aksesibilitas sebanyak 1 aspek, dan biota berbahaya sebanyak 1 jenis. Kesesuaian wisata diving di Perairan P. Soreh pada setiap stasiun merupakan kawasan yang sesuai untuk dilakukan pengembangan ekowisata diving. Daya dukung terumbu karang untuk pengembangan ekowisata diving di Perairan P. Soreh pada setiap stasiun sesuai untuk dilakukan pengembangan wisata diving.

ZIPLAS: Zooplankton Index for Polish Lakes’ Assessment: a new method to assess the ecological status of stratified lakes

Zooplankton is widely recognized as a key component of pelagic ecosystems and forms the basis for major trophic webs. Although zooplankton has often been used as an indicator of trophic state, it has not been included as an obligatory element of the water assessment systems compliant with the Water Framework Directive. This article introduces the Zooplankton Index for Polish Lakes’ Assessment (ZIPLAS) as a new method to assess the ecological status of stratified lakes based on the zooplankton community. The ZIPLAS evaluates three aspects of zooplankton communities, namely, taxonomic composition and abundance, diversity of the zooplankton community, and stressor-sensitive species, which are combined into a multimetric index. Following are the metrics used to compose multimetric ZIPLAS: percentage share of the Rotifer species indicative of high trophy in the indicative group’s number (IHTROT; %), ratio of Calanoida to Cyclopoida individual numbers (CA/CY), percentage of tecta form in the population of Keratella cochlearis (TECTA; %), Margalef’s index (d), and zooplankton abundance (NZOL; ind./L). ZIPLAS responds clearly to eutrophication indicators—the strongest with Secchi disc visibility (Spearman’s rank correlation R = 0.86) and slightly weaker with the expressed by total phosphorus (R = -0.74), total nitrogen (R = 0.68) and the catchment pressure expressed by the nutrient loads generated by different types of land use (R = -0.58).

Study of Limnological Status of Two Selected Floodplain Wetlands of West Bengal

Limnology is the study of all aquatic systems, both lentic and lotic fresh, fresh, and saline including lakes, wetlands, marshes, bogs, ponds, reservoirs, streams, rivers, oceans, etc. about their physical, chemical, and biological characteristics. Among this phytoplankton, Zooplankton, periphyton, benthos are a minute aquatic free-floating microscopic organism, which acts as a larger food source of larval and higher vertebrates and invertebrates including carnivorous and omnivorous fishes. They are related to the growth of juvenile fishes and are also play important role in the transfer of energy from the primary phytoplankton to higher trophic levels. The plankton community fluctuates according to the physicochemical parameters and the relative environment of the water body especially the Rotifers as they are known to change immediately along with the change in water quality . Realizing the importance of floodplain wetlands and the paucity of literature on the limnology of this ecosystem present investigation was carried out in two floodplain wetlands having characteristics of open (Kole beel, an ox-bow lake formed near Somra Bazar in Hooghly district), and closed beel Suguna beel situated in Nadia District of West Bengal) system during the period 2011–2013. The physicochemical parameters of the investigated beels' water and soil were, for the most part, favorable for planktonic development. It has an alkaline pH of 7.5–8.4 and is alkaline. The dissolved oxygen content and Secchi Disc transparency values indicate that the water is in excellent condition. The water was moderately hard, with only trace amounts of nutrients present. Seasonal fluctuations in the water column were apparent, and they were mainly attributable to replenished supplies and volume. The plankton population of the studied ecosystem was made up of a mixed and healthy population of diverse fauna. The greatest diversity was observed during the winter season, when favorable temperature, dissolved oxygen, and other physicochemical parameters of water, as well as optimal solar penetration, coincided. In a closed system (Suguna), the richness of planktonic structure resulted in higher fish production (1570.05 kg/ha/yr) than in an open system (Kole) (384.4 kg/ha/yr). The status of floodplain wetlands was determined to be eutrophic based on various Physico-chemical and biological parameters.

Importance of light status on phytoplankton biomass in the turbid Bisan Strait, Japan: results from a high-frequency sampling study

The dynamics of phytoplankton biomass in the vertically mixed south-eastern part of the Bisan Strait, in the Seto Inland Sea of Japan, may be considered to be strongly dependent not only on nutrients but also on light status. This was investigated by examining variations in chlorophyll-a (Chl-a), nutrients, and Secchi-disc depth through high-frequency sampling (a mean of once every 1.7 days) at the same station from April to October 2019. Precipitation during the Japanese rainy season (East Asian monsoon rains) was associated with a decrease in salinity from 32 to 31 in late July. The highest concentration of dissolved inorganic nitrogen (DIN), the most deficient nutrient, also was recorded in late July in association with seasonal precipitation. However, the measured Chl-a peak (max. 4 μg l−1) in early August was not as high as expected, possibly due to low water clarity. A relatively small but substantial peak of DIN (max. 4 μM) was recorded in mid-August, which coincided with the passing of a typhoon. The small peak of DIN coupled with higher water clarity thereafter was followed by a phytoplankton bloom from mid-August to early September, at which the highest Chl-a (7 μg l−1) occurred. It is suggested that increased light penetration enhanced the efficiency of nutrient assimilation and thereby triggered the late-summer phytoplankton bloom. In contrast to the adjacent stratified areas, light rather than nutrient status appears to be the key determinant for the onset of phytoplankton blooms in the Bisan Strait.

Plankton composition of Hakaluki Haor of Moulvibazar, Bangladesh

In the present study, physicochemical and biological variables related to the water quality of Hakaluki Haor were studied. Three study stations viz. Bakshimul, Jalabeel and Dudhai were investigated because of an event of mass scale of dead fish and other aquatic organisms were reported. The stations had water depths from 2.74 - 5.13 m and Secchi Disc Transparency were 0.74 - 1.91 m. The air and water temperature among the three stations ranged from 28.2 - 30.4°C and 21.8 - 28.8°C, respectively. TDS ranged from 35 - 42 mg/l, while the electric conductivity of water showed 40 - 50 μS/cm. SRP, nitrate and SRS ranged from 10.68 - 12.32 μg/l, 0.116 - 0.122 mg/l and, 16.08 - 35.42 mg/l, respectively. The concentration of DO was very poor which ranged from 2.8 - 5.4 mg/l. In all the three studied stations, the free CO2 concentration was 0.096 mg/l. Chlorophyll-a value was moderate in all the three stations (ranged within 34.67 and 40.60 μg/l). The phaeopigment concentration was low and ranged from 1.51- 8.72 μg/l among the studied stations. Concentration of ammonia was much higher (1.03 - 1.72 mg/l) than the standard value for Bangladesh (0.5 mg/l). From this analysis, it is observed that during fish kill event the concentration of ammonia was higher with low DO content which might have resulted because of the decomposition of upper foliar parts of the rice plant due to the sudden inundation. Gross α and β counts were found to be 0.01 and 0.10 Bq/l in the Haor water at the time of fish kill. From the planktonic community, 16 phytoplanktons from green algae, 14 euglenoids, 5 diatoms, 5 dinoflagellates and 12 zooplankton species were recorded. A shift in the pH of the Haor water from acidic to alkaline might have occurred during the last 3 decades. A detailed limnological study covering the climatic seasons of Bangladesh has been recommended to be carried out for Hakaluki Haor. Dhaka Univ. J. Biol. Sci. 30(1): 69-78, 2021 (January)

Polyculture of Largemouth Bass (Micropterus salmoides) with Blue Tilapia (Oreochromis aureus): Using Tilapia Progeny as Forage

In this study, five, 0.04-ha ponds were stocked with advanced size largemouth bass fingerlings at densities of 124, 247, 494, 988, and 1136/ha. Tilapia brood fish were stocked at densities of 590/ha (male: female ratio was 1:3). Pond trials were conducted for a 6-month period, June to December 1985. Bass survival ranged from 40 to 89%. Bass stocked at densities 494/ha (low density) grew significantly larger than those at 988/ha (high density). Mean bass weights and percent weight gains at harvest in low versus high density ponds were 593 g and 3,318% and 120 g and 329%, respectively. High density bass ponds produced larger tilapia broodfish at harvest. The number of juvenile tilapia surviving in low density bass ponds was substantially greater (20,000 juveniles/ha) than in high density bass ponds (99 and 420 juveniles/ha). The higher survival of tilapia juveniles in low density bass ponds was the apparent cause of significantly higher turbidity (determined from secchi disc measurements) in these ponds. The results of this study suggest that forage/predator ratios, based on densities of female tilapia broodfish to bass, of 0.7 and 1.4 are suitable for controlling spawn and producing large tilapia or for producing large bass, respectively.

Assessment of Water Buffer Capacity of Two Morphometrically Different, Degraded, Urban Lakes

The research was conducted in Karczemne Lake (area, 40.4 ha; maximum (max.) depth, 3.2 m) and Klasztorne Małe Lake (area, 13.7 ha; max. depth, 20.0 m) located in the Kashubian Lake District (Northern Poland). From the beginning of the 1950s, these reservoirs have received municipal and storm wastewater. The long-term process of lake contamination has shaped the specific buffer capacity conditions and influenced the circulation of carbonate and bicarbonate in the water of these ecosystems. Extremely high concentrations of nutrients (Karczemne Lake: max. total phosphorous (TP) level, 7.5 mg P L−1; max. total nitrogen (TN) level, 5.6 mg N L−1; Klasztorne Małe Lake: max. TP level, 20.6 mg P L−1; max. TN level, 43.3 mg N L−1) have caused very intensive primary production processes (Karczemne Lake: max. chlorophyll-a level, 193.40 µg m−3; max. Secchi disc visibility, 0.85 m; Klasztorne Małe Lake: max. chlorophyll-a level, 160.01 µg m−3; max. Secchi disc visibility, 1.15 m). In the polymictic Karczemne Lake, the pH value of all water columns exceeded 10.0 (max. pH, 10.41), and in the meromictic Klasztorne Małe Lake, the pH of the surface water layers oscillated around 9.5. In the polymictic Karczemne Lake, despite intensive photosynthesis, the calcium content and alkalinity were similar throughout the whole water column due to constant circulation. In the meromictic Klasztorne Małe Lake, during the growing season, a decrease in calcium concentration and alkalinity of the surface water layers and an increase in calcium concentration at the bottom were noted.