Abundance and Composition of Zooplankton (Copepoda, Cladocera, Rotifera) in Lake Taal: Potential Impact of Intensive Size-Selective Predation by the Freshwater Sardine, Sardinella tawilis (Herre 1927)

Zooplankton are considered to be important members of the lake ecosystem. The abundance and composition of which are due to several factors, for example, the impact of intensive size-selective predation by planktivorous fishes residing in the lake. In this study, the abundance and composition of zooplankton found in the vicinity of Isla Napayun - a known fishing ground of the freshwater sardine, Sardinella tawilis (Herre 1927) was analyzed using samples taken from vertical plankton tows from the 10 and 20 m depths in 2 sampling sites from the said area. These were then compared with the stomach contents of S. tawilis taken during the same period. Results show that there were 4 genera of Copepoda, 4 genera of Cladocera and 2 genera of Rotifera found in the plankton tows that were analyzed. Of these, the nauplius larvae of the copepods were noted to be the most abundant followed by the rotifer Brachionus spp. Analysis of the stomach contents of the collected S. tawilis samples revealed a zooplankton diet that was composed of 90% Copepoda with the remaining 10% being made up of the Cladocera and Rotifera. These results indicate that small-bodied organisms dominate the lake. This is indicative of intensive size-selective predation by the S. tawilis on the zooplankton population of the area. This is further validated by the high preference of S. tawilis for Copepoda, which is the largest of the 3 groups (in terms of size) in the samples that were analyzed in spite of the fact that small-bodied zooplankton dominate the zooplankton community during the entire sampling period. The zooplankton found in this particular area of Lake Taal has been observed to be highly influenced by intensive size selective preference of planktivores such as the S. tawilis for bigger zooplankton

Abundance and Composition of Zooplankton (Copepoda, Cladocera, Rotifera) in Lake Taal: Potential Impact of Intensive Size-Selective Predation by the Freshwater Sardine, Sardinella tawilis (Herre 1927)

Zooplankton are considered to be important members of the lake ecosystem. The abundance and composition of which are due to several factors, for example, the impact of intensive size-selective predation by planktivorous fishes residing in the lake. In this study, the abundance and composition of zooplankton found in the vicinity of Isla Napayun - a known fishing ground of the freshwater sardine, Sardinella tawilis (Herre 1927) was analyzed using samples taken from vertical plankton tows from the 10 and 20 m depths in 2 sampling sites from the said area. These were then compared with the stomach contents of S. tawilis taken during the same period. Results show that there were 4 genera of Copepoda, 4 genera of Cladocera and 2 genera of Rotifera found in the plankton tows that were analyzed. Of these, the nauplius larvae of the copepods were noted to be the most abundant followed by the rotifer Brachionus spp. Analysis of the stomach contents of the collected S. tawilis samples revealed a zooplankton diet that was composed of 90% Copepoda with the remaining 10% being made up of the Cladocera and Rotifera. These results indicate that small-bodied organisms dominate the lake. This is indicative of intensive size-selective predation by the S. tawilis on the zooplankton population of the area. This is further validated by the high preference of S. tawilis for Copepoda, which is the largest of the 3 groups (in terms of size) in the samples that were analyzed in spite of the fact that small-bodied zooplankton dominate the zooplankton community during the entire sampling period. The zooplankton found in this particular area of Lake Taal has been observed to be highly influenced by intensive size selective preference of planktivores such as the S. tawilis for bigger zooplankton

Mixing Regimes in a Cluster of Seven Maar Lakes in Tropical Monsoon Asia

The 7 maar lakes of San Pablo are a cluster of small volcanic lakes on Luzon Island; Philippines. These lakes; which are heavily utilized for aquaculture and ecotourism; usually experience fish kills that coincide with the northeast monsoon (NEM). This study explores limnophysical processes; particularly mixing regimes; in the lakes in relation to prevailing monsoons. We monitored monthly vertical and seasonal profiles of water temperature; salinity; conductivity; and dissolved oxygen from October 2016 to December 2018. Three types of mixing regimes were observed among the lakes; which have similar surface areas but different depths: polymixis in the shallowest; warm monomixis in lakes with intermediate depth; and meromixis in the deepest. A boundary between monomixis and meromixis was identified between 36 and 62 m depth. Monthly monitoring showed seasonal mixing occurred exclusively during the NEM (Nov–Apr). We also incorporated meteorological data into the model and performed multiple regression analysis for each lake to determine the best predictor: lake stability; as indicated by the Schmidt stability (ST). A between-lake comparison showed lake stability was strongly correlated with both air temperature and wind speed; suggesting these 2 meteorological variables are involved in establishing thermal stratification in the lakes during the southwest monsoon. This study provides insights for adaptive lake management and projections of climate impacts on these understudied tropical lake ecosystems in Southeast Asia

Freshwater microcrustaceans (Cladocera: Anomopoda and Ctenopoda, Copepoda: Cyclopoida and Calanoida) in the highly urbanized Metropolitan Manila area (Luzon, Philippines)

Despite the increasing interest in studying Cladocera and Copepoda in Philippine freshwaters, there is a need to update our knowledge on its taxonomy and distribution in highly urbanized areas, such as Metropolitan Manila. This paper presents an updated listing of freshwater microcrustaceans and their distribution in Metropolitan Manila, considering the continued deterioration of water quality and increased urbanization in many areas since the last comprehensive study on these taxa in 1950s. We collected water samples from 33 freshwater sites in Metropolitan Manila and 23 of which were found to contain microcrustacean zooplankton. A total of 13 species were identified including two new locality records for C. cornuta and D. dubium in Pasig River. All 8 cladocerans, we identified have already recorded in previous studies while 3 cyclopoid copepods are new records for Metropolitan Manila. Furthermore, 16% of all known freshwater microcrustacean zooplankton species in the Philippines are found in Metropolitan Manila, including the Luzon-endemic Filipinodiaptomus insulanus collected from man-made reservoirs in less-disturbed habitats (an urban wildlife park, golf course and eco-park). Other identified species such as Thermocyclops taihokuensis may serve as indicator for high levels of nutrient. These results point to the importance of monitoring urban aquatic biodiversity for their potential in determining aquatic ecosystem health and of maintaining urban aquatic sanctuaries which may serve as alternative habitat for flora and fauna in rapidly developing urban centers such as Metropolitan Manila

Fig. 3 in The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines)

Fig. 3. Mean monthly biomass (μg / l) of common zooplankton species from the north and south basins of Lake Taal for the year 2008.Published as part of <i>Papa, Rey Donne S. & Zafaralla, Macrina T., 2011, The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines), pp. 1-7 in Raffles Bulletin of Zoology 59 (1)</i> on page 4, DOI: <a href="http://zenodo.org/record/10106648">10.5281/zenodo.10106648</a&gt

An overview of the limnetic Cyclopidae (Crustacea, Copepoda) of the Philippines, with emphasis on Mesocyclops

Approximately 120 (sub)species of Cyclopidae have been reported from South and Southeast (SE) Asia, where the Philippine archipelago – with 16 (including two endemic) taxa – is one of the least explored parts of the region. Our study, part of current efforts to assess freshwater biodiversity, was undertaken to update the diversity and geographic distribution of the cyclopid copepods living in the limnetic zone of the freshwater lakes in the Philippines. Examination of the samples from 22 lakes in five islands (Luzon, Mindoro, Cebu, Leyte and Mindanao) revealed a novel species from lake Siloton (Mindanao), Mesocyclops augusti n. sp. The new species can be distinguished from the congeners by the surface ornamentation of the hindgut, among others. The same character state was found in a Mesocyclops from North Vietnam, which is provisionally identified as M. augusti n. sp., though the Vietnam and Mindanao specimens differ in a few (yet polymorphic in the close relatives) characters. Mesocyclops microlasius Kiefer, 1981 endemic to the Philippines is redescribed, based on females and males from lake Paoay (North Luzon). Sister relationships of M. augusti n. sp. and M. microlasius were tested in a phylogenetic analysis that included the closely related Old World representatives of the genus. The max. parsimony trees show M. dissimilis Defaye et Kawabata, 1993 (East Asia) as the closest relative of M. augusti n. sp. (Mindanao, Vietnam), and support sister relationship between M. geminus Holynska, 2000 (East Borneo) and M. microlasius (Luzon, Mindanao). A mainland clade (M. francisci, M. parentium, M. woutersi, M. dissimilis, M. augusti) appears in most reconstructions; all members of the clade occur in continental Asia though some species also live in islands that have never been connected to the SE Asian shelf. In most trees with the mainland clade the insular taxa (M. microlasius, M. geminus, M. friendorum) form either a paraphyletic (basal to mainland) or monophyletic sister group of the mainland clade. We also established the first records of Thermocyclops taihokuensis (Harada, 1931) in the Philippines (Luzon), so far known from East and Central Asia. In all, 11 taxa [Mesocyclops (4), Thermocyclops (4), Microcyclops (1), Tropocyclops (1) and Paracyclops (1)] including only one endemic species (M. microlasius) have so far been found in the limnetic waters. We expect significantly higher diversity and higher rate of endemism of the freshwater cyclopids in the littoral (paludal) and subterranean habitats in the Philippines

Fig. 1 in The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines)

Fig. 1. Map of Lake Taal with the six sampling sites (NB – North Basin, SB – South Basin). The insert shows the location of Lake Taal and the other lakes mentioned in the text (P – Lake Paoay, Lb – Lake Laguna de Bay, N – Lake Naujan and Ln – Lake Lanao).Published as part of <i>Papa, Rey Donne S. & Zafaralla, Macrina T., 2011, The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines), pp. 1-7 in Raffles Bulletin of Zoology 59 (1)</i> on page 3, DOI: <a href="http://zenodo.org/record/10106648">10.5281/zenodo.10106648</a&gt

Fig. 2 in The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines)

Fig. 2. Average abundance (Ind. / l) and number of species of Copepoda, Cladocera and Rotifera from the upper 40 m in Lake Taal in the year 2008. The Copepoda were grouped into nauplii, Calanoida and Cyclopoida.Published as part of <i>Papa, Rey Donne S. & Zafaralla, Macrina T., 2011, The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines), pp. 1-7 in Raffles Bulletin of Zoology 59 (1)</i> on page 3, DOI: <a href="http://zenodo.org/record/10106648">10.5281/zenodo.10106648</a&gt