Abundance Of Cyclopoid Copepods Research Articles

Cyclopoid copepods as indicators of trophic level in South American reservoirs: A new perspective at species level based on a wide spatial-temporal scale

Aiming to identify efficient indicators for reservoir water quality, the abundance of cyclopoid copepods, 11 limnological variables, and a modified trophic state index (TSI) for tropical/subtropical reservoir systems were studied in 30 different reservoirs in South America. A total of 331 fieldwork campaigns, originated from six different studies on a wide spatial–temporal scale were analyzed. Samplings included small to large reservoirs (varying between 6 and 2250 km2 area) with oligo, meso and eutrophic conditions, and places with punctual eutrophication from fish cage farms. Spatial scale ordination was relevant for variables and reservoirs, but the temporal scale was also important in all analyses, positioning the same reservoir sampled in different years contrasting correlations in terms of species and variables. Principal component analysis consistently indicated the importance of chlorophyll, nutrients (phosphorus and nitrogen), turbidity, transparency, and depth for proper ordination of reservoirs according to their trophy. Of all the 13 cyclopoid species identified, ten were planktonic and at the end, after conclusive statistical correlation analysis, five species were selected as efficient water quality indicators. Redundancy analysis related different species with different trophic aspects: Acanthocyclops robustus, Microcyclops anceps and Tropocyclops prasinus were positively associated with chlorophyll and inversely associated with water transparency, Thermocyclops decipiens and T. inversus with electrical conductivity, and slightly associated with chlorophyll and total nutrients (phosphorus and nitrogen), and finally Thermocyclops minutus was positively correlated with transparency. Spearman correlations indicated that only T. inversus abundance was correlated with water temperature, but T. decipiens was not correlated with TSI, which is intriguing because this species has been commonly associated with eutrophic waters. Despite tolerate a wide range of trophic conditions, as pointed in RDA, T. decipiens seems to be replaced by other more resistant species when trophic conditions become too high – hypereutrophic environments. Four other selected species were correlated with TSI, and T. minutus was negatively correlated, confirming its association with oligotrophic waters. From all species found, we conclude that A. robustus, M. anceps, T. prasinus, T. decipiens and T. minutus are good indicators of trophic state level in South American reservoirs.

Temperature, discharge and development shape the larval diets of threatened green sturgeon in a highly managed section of the Sacramento River

AbstractFeeding at early fish life stages is a key determinant of survival to recruitment. To understand the environmental and developmental determinants of early life stage feeding in ESA‐threatened green sturgeon (Acipenser medirostris), we performed a diet study in a highly managed section of California's Sacramento River, where temperature and discharge are controlled by dam releases. Utilising field collections from 2012 to 2016, we assessed the impacts of temperature, discharge and morphological development on the composition and number of prey items in larval green sturgeon diets. Results show that there are more empty stomachs at colder temperatures. Higher discharge conditions decreased prey taxon richness and counts, especially the abundance of cyclopoid copepods in diets. Fish smaller than 30 mm had teeth on the oral jaws and showed a strong reliance on zooplankton prey. The developmental loss of teeth in fish greater than 30 mm was associated with decreased zooplankton consumption and increased richness of benthic macroinvertebrates in diets. Our results show that river management through dam releases has the potential to impact the earliest life stage of green sturgeon by reducing the prevalence of favoured zooplankton prey in diets.

Responses of cyanobacteria to herbivorous zooplankton across predator regimes: who mows the bloom?

Summary The massive growth of large, toxic cyanobacteria in eutrophic waters has traditionally been explained by their evolution of defences to herbivorous zooplankton. These conclusions come mostly from studies using the large‐bodied cladoceran Daphnia as a grazer model. In contrast, very little is known about the effects of other zooplankters such as copepods and small cladocerans that, unlike Daphnia, often coexist with cyanobacterial blooms and under high levels of fish predation. We performed a series of grazing experiments during a cyanobacterial bloom in a eutrophic lake, subject to decreasing predation on zooplankton (removal of cyprinid fish). We also used long‐term observational data to analyse the response of cyanobacteria to changes in abundance, body size and biomass of the naturally, coexisting zooplankton community across different predator regimes. A natural grazer community, dominated by selective herbivores like calanoid and cyclopoid copepods, positively affected cyanobacterial growth in early summer at low cyanobacterial densities. However, cyclopoid copepods and small cladocerans suppressed the growth of Anabaena, Microcystis and Planktothrix species under bloom conditions in late summer, with the exception of the highly toxic Microcystis botrys. Long‐term observational data support the results from the grazing experiments regarding the potential capacity of the natural zooplankton community to suppress cyanobacterial growth, especially of the dominant taxon Microcystis (including the most toxic species, M. botrys). In particular, these results suggest that direct grazing may contribute significantly to the observed 72% decrease in Microcystis biomass through a 111% increase in abundance of cyclopoid copepods, and an 18% increase in body size of cyclopoid copepods and a 31% increase in body size of the generalist feeder Daphnia, during the biomanipulation. Together, these results suggest that, within the complex interactions brought about by trophic cascades, direct grazing by the coexisting zooplankton community is a strong driver regulating cyanobacterial growth in eutrophic lakes and that this can display contrasting effects, both seasonally and under different levels of fish predation. Importantly, we show that herbivory may be enhanced along a gradient of decreasing fish predation by the combined action of copepods (selective herbivores) and Daphnia (generalist herbivores).

Diversity and abnormalities of cyclopoid copepods around hydrothermal vent fluids, Kueishantao Island, north-eastern Taiwan

The diversity and abundance of cyclopoid copepods were investigated at four stations along the hydrothermal vent at Kueishantao Island, north-eastern Taiwan. Zooplankton samples were collected by surface tows. Qualitatively, 21 species of cyclopoids belonging to five genera and three families were observed. Our analysis revealed a number of abnormal protrusions (TLAs) on cyclopoid copepods, which were more frequent on the dorsal body surface and in members of the family Corycaeidae. The number of TLAs was highest at the hydrothermal vent plume (HVP) zone and among adult copepods. The potentially high levels of toxic minerals erupting from the hydrothermal vents as well as low pH and high temperatures may weaken the copepods' exoskeletons, thereby increasing susceptibility to infections, indicated by the HVP-related increase of tumoural processes. It is suggested that some of these abnormalities are related to the occurrence of symbiotic tantulocarids, a topic yet to be studied in this interesting environment.

Existing in plenty: abundance, biomass and diversity of ciliates and meiofauna in small streams

Summary1. The ciliate and metazoan meiofaunal assemblages of two contrasting lowland streams in south‐east England were examined over the period of a year, using a high taxonomic resolution. Monthly samples were taken from an oligotrophic, acid stream (Lone Oak) and a circumneutral, nutrient‐rich stream (Pant) between March 2003 and February 2004.2. We assessed the relative importance of ciliates and rotifers within the small‐sized benthic assemblage with respect to their abundance, biomass and species richness. In addition, we examined the influence of abiotic and biotic parameters and season on the assemblage composition at two levels of taxonomic resolution (species and groups).3. Ciliates dominated the assemblages numerically, with maximum densities of over 900 000 and 6 000 000 ind. m−2 in Lone Oak and Pant respectively. Rotifers and nematodes dominated meiofaunal densities, although their contribution to total meiofaunal biomass (maxima of 71.9 mgC m−2 in Lone Oak and of 646.8 mgC m−2 in the Pant) was low and rotifer biomass equalled that of ciliates.4. Although the two streams differed in terms of total abundance of ciliates and meiofauna and shared only 7% of species, the relative proportion of groups was similar. Sediment grain size distribution (the percentile representing the 0.5–1 mm fraction) was correlated with assemblage structure at the species level, revealing the tight coupling between these small organisms and their physical environment. Seasonal changes in the relative abundance of groups followed similar patterns in both streams, and were correlated with the abundance of cyclopoid copepods and temperature.5. Information on these highly abundant but often overlooked faunal groups is essential for estimates of overall abundance, biomass, species richness and productivity in the benthos, and as such has important implications for several areas of aquatic research, e.g. for those dealing with trophic dynamics.

Influence of drought on algal biofilms and meiofaunal assemblages of temperate reservoirs and rivers

The role of hydrological droughts in shaping meiofauna abundance through alterations in biofilm biomass and composition was investigated. In January 2005, continental Portugal was under a moderate to severe drought resulting from a 40% to 60% decrease in rainfall during the previous 12 months relative to the long-term average (1961–1990). Reservoir capacity was reduced by 30–50% relative to average values and the width of streams was reduced by 20–80% in the Zezere River Basin (central Portugal). Algal biomass and algal class composition of biofilms was assessed through quantification of algal pigments in three reservoir and six river locations. During drought, habitat alterations are expected to be sharp in rivers while, in the absence of water quality deterioration, the habitat characteristics of reservoirs are expected to remain fairly unaffected. Chlorophylls and carotenoid pigments were extracted from biofilm samples and analysed using high performance liquid chromatography (HPLC). In the winter of 2003, during the period of average rainfall, biofilm biomass did not exceed 5 μg chlorophyll a cm−2 at any location. River biofilm biomass was roughly half of that measured in the reservoirs. In the winter of 2005 (drought), biofilm biomass increased by more than 5-fold in river locations and remained low or decreased in the reservoirs. Algal biofilms were either dominated by Bacillariophyceae or by Chlorophyceae regardless of the existence of drought. The relative contribution of Bacillariophyceae to total biofilm biomass was higher during the drought than under average hydrological conditions. The abundance of harpacticoids, cladocerans and ostracods was favoured by the drought only in the reservoirs where an increase in diatom proportion in biofilms was observed. The increase in the abundance of cyclopoid copepods, turbellarians, nematodes and chironomids in rivers during the drought could be explained by algal class composition and biomass of biofilms and environmental variables (organic matter sediment content, phosphorus availability content and sediment granulometry). The hydrological drought appears to regulate meiofauna abundance only in river locations, possibly through the promotion of the growth of biofilms and the availability of organic matter deposited in rivers during the drought.

Infection rate, distribution and relative abundance of cyclopoid copepods in dracunculasis endemic foci of Ebonyi State, Nigeria

Between February 2001 and January 2002 studies on the infection rates, distribution and relative abundance of cyclopoid copepods were carried out on 15 sources of drinking water, which were sources commonly used in some selected guinea worm endemic villages in 3 L.G.As (Ebonyi, Ikwo, izzi) of Ebonyi State, Nigeria. In all, a total of 6,502 cyclops were collected of which 132 (2.03%) were infected with the larvae of Dracunculus medinensis . Five different species of Cyclops were encountered and identified. These include: Thermocyclops Oblongatusnigerianus, Mesocyclopseaquatorialis, Tropocyclopsconfinis and Mesocyclopsespericonis . However, only T. oblongatusnigerianus and M. aequatorialis harboured infected larvae of the worm. Infected cyclopoid copepods population was highest in March 2001 with density of 1017/liter while August, which is the peak of the raining season, had the lowest Cyclops density with none infected. A positive correction (r = +0.1) was established between vector infectivity and prevalence of the disease in the area. The epidemiological implications of these observations in the control of dracunculiasis in South Eastern Nigeria are stressed. Keywords : cyclopoid copepods, infection rate, relative abundance, dracunculiasis, Nigeria International Journal of Natural and Applied Sciences Vol. 1(1) 2005: 40-45

Littoral microcrustacea in Lake 302S in the Experimental Lakes Area of Canada: acidification and recovery

Summary 1 The littoral microcrustacean community (Cladocera and Copepoda) was examined from 1989 to 1991 in a lake experimentally acidified to pH 4.5, and from 1992 to 1997 during the early stages of pH recovery. 2 Cladoceran abundance declined significantly from 1989 to 1991 (pH 4.5), but species richness did not change. Acantholeberis curvirostris, Simocephalus serrulatus, Latona spp. (Latona setifera, L. parviremis), and all species of chydorid Cladocera declined markedly in abundance while at pH 4.5. The abundance of cyclopoid copepods was low and Ceriodaphnia and calanoid copepods were absent. 3 Recovery of the community was subsequently monitored as pH was incrementally changed to a target pH 5.1 in 1992 and 1993, and to 5.8 in 1994–97. Species richness remained unchanged. Chydorid cladocerans remained at low abundance in 1992, and only Chydorus cf. brevilabris increased substantially from 1993 to 1996. Non-chydorid Cladocera increased in abundance in 1992, declined again in 1993, then gradually increased (mainly due to Ophryoxus gracilis) in 1994–96. All species declined in 1997 as minnows recolonized the lake. The calanoid copepod Leptodiaptomus minutus was present in low numbers in 1997. 4 The microcrustacean community in the littoral zone of Lake 302S has not yet shown consistent signs of recovery from acidification.

Species assemblages of cyclopoid Copepoda from Mantecal, Venezuela

A 14 year monitoring of species composition and abundance of cyclopoid copepods throughout the rainy and dry seasons in a flooded savanna at Mantecal, Apure State, Venezuela, is presented. Two characteristic habitats within these water bodies were selected: the open center of small ponds free of emergent vegetation and the surrounding flooded grassland. In total, 13 species were registered, all of which appeared in the flooded grassland and 11 of which occurred in the open water. Ten species were common for the two habitats during the dry season. The highest abundance was found in flooded grassland during the dry season. Eight species showed abundances greater than 1.0 individual per liter in flooded grassland during both seasons; 3 and 7 species were this abundant in the open water during rainy and dry seasons, respectively. Mesocyclops meridianus and Microcyclops varicans were the most abundant species in both habitats and seasons, while Thermocyclops decipiens was the dominant species during rainy season in open water. Principal component analysis indicates that the important species were positively correlated between them (sharing habitat and season).

Changes in the abundance and composition of cyclopoid copepods following fish manipulation in eutrophic Lake Væng, Denmark

SUMMARY 1. The seasonal cycle of cyclopoid copepods during and following an approximately 50% reduction in planktivorous fish biomass was studied in shallow, eutrophic Lake Vaeng, Denmark, from 1986 to 1990. 2. The dominant cyclopoid copepods changed from Cyclops vicinus and Mesacyclops leuckarti during 1986–1989 to M. leuckarti and Megacyclops viridis in 1990. The abundance of cyclopoid copepods gradually increased from 1986 to 1988–89, decreased in autumn 1989 and markedly decreased in 1990. 3. The increase in the abundance of cyclopoid copepods from 1986 to 1988 is attributed mainly to the reduction in fish predation pressure, there being no concomitant increase in edible phytoplankton. The appearance of M. viridis in 1990, and the general decrease in cyclopoid copepod density in autumn 1989 and in 1990, are attributed to the appearance of submerged macrophytes. 4. Temperature, predation and availability of edible phytoplankton appear to determine whether C. vicinus or M. leuckarti dominates the cyclopoid copepod population of eutrophic Lake Vaeng.