Seasonal Density Research Articles

Adverse moisture events predict seasonal abundance of Lyme disease vector ticks (Ixodes scapularis).

BackgroundLyme borreliosis (LB) is the most commonly reported vector-borne disease in north temperate regions worldwide, affecting an estimated 300,000 people annually in the United States alone. The incidence of LB is correlated with human exposure to its vector, the blacklegged tick (Ixodes scapularis). To date, attempts to model tick encounter risk based on environmental parameters have been equivocal. Previous studies have not considered (1) the differences between relative humidity (RH) in leaf litter and at weather stations, (2) the RH threshold that affects nymphal blacklegged tick survival, and (3) the time required below the threshold to induce mortality. We clarify the association between environmental moisture and tick survival by presenting a significant relationship between the total number of tick adverse moisture events (TAMEs - calculated as microclimatic periods below a RH threshold) and tick abundance each year.MethodsWe used a 14-year continuous statewide tick surveillance database and corresponding weather data from Rhode Island (RI), USA, to assess the effects of TAMEs on nymphal populations of I. scapularis. These TAMEs were defined as extended periods of time (>8 h below 82% RH in leaf litter). We fit a sigmoid curve comparing weather station data to those collected by loggers placed in tick habitats to estimate RH experienced by nymphal ticks, and compiled the number of historical TAMEs during the 14-year record.ResultsThe total number of TAMEs in June of each year was negatively related to total seasonal nymphal tick densities, suggesting that sub-threshold humidity episodes >8 h in duration naturally lowered nymphal blacklegged tick abundance. Furthermore, TAMEs were positively related to the ratio of tick abundance early in the season when compared to late season, suggesting that lower than average tick abundance for a given year resulted from tick mortality and not from other factors.ConclusionsOur results clarify the mechanism by which environmental moisture affects blacklegged tick populations, and offers the possibility to more accurately predict tick abundance and human LB incidence. We describe a method to forecast LB risk in endemic regions and identify the predictive role of microclimatic moisture conditions on tick encounter risk.

Parasitoides do bicudo Anthonomus grandis e predadores residentes em algodoeiro pulverizado com caulim

Simultaneous use of control methods is essential to reach success in managing arthropod pests. The current study investigated the effect of kaolin application on resident predators in the cotton plant canopy and parasitism of boll weevil on abscised squares in the field, and parasitism of boll weevil in the laboratory. Predators Araneae, Formicidae, Chrysopidae, and Coccinellidae showed similar seasonal densities for kaolin-treated and untreated cotton fields as well as the emergence rate of the parasitoids Bracon vulgaris Ashmead (Hymenoptera: Braconidae) and Catolaccus grandis Burks (Hymenoptera: Pteromalidae) from abscised field-collected structures. Under laboratory conditions, the parasitism of boll weevil larvae infesting squares was similar when treated and untreated squares with kaolin were offered to the parasitoid under free choice test. Therefore, the results show that spraying cotton fields with kaolin does not affect the natural biological control by parasitoids of boll weevil and pink bollworm and resident predators naturally occurring in cotton fields.

A seasonal, density‐dependent model for the management of an invasive weed

The population effects of harvest depend on complex interactions between density dependence, seasonality, stage structure, and management timing. Here we present a periodic nonlinear matrix population model that incorporates seasonal density dependence with stage-selective and seasonally selective harvest. To this model, we apply newly developed perturbation analyses to determine how population densities respond to changes in harvest and demographic parameters. We use the model to examine the effects of popular control strategies and demographic perturbations on the invasive weed garlic mustard (Alliaria petiolata). We find that seasonality is a major factor in harvest outcomes, because population dynamics may depend significantly on both the season of management and the season of observation. Strategies that reduce densities in one season can drive increases in another, with strategies giving positive sensitivities of density in the target seasons leading to compensatory effects that invasive species managers should avoid. Conversely, demographic parameters to which density is very elastic (e.g., seeding survival, second-year rosette spring survival, and the flowering to fruiting adult transition for maximum summer densities) may indicate promising management targets.

Seasonal density dynamics and distribution of brachyuran crab larvae (Decapoda: Brachyura) in Amursky and Ussuriysky bays, Sea of Japan

The species composition, period of occurrence, density, and distribution of brachyuran crab larvae (Decapoda: Brachyura) in the Amursky and Ussuriysky bays (Sea of Japan) were studied in May–October 2007 and 2008. The larvae of this group were not numerous, with peak densities occurring in July at maximum water temperatures. The average brachyuran larvae density was up to 126.9 ind./m3 in Ussuriysky Bay and 68 ind./m3 in Amursky Bay; the contribution of Brachyura to all decapod larvae reached 80–90%. In Amursky Bay, the highest density of brachyuran larvae (up to 584 ind./m3) was observed along the western coast over depths to 20 m; in Ussuriysky Bay, the larval density was highest (up to 1817 ind./m3) in the shallowwater northern part and progressively decreased with depth. Larvae of 18 brachyuran species were found in plankton samples. In Amursky Bay, intertidal crab larvae of the genus Hemigrapsus dominated, Eriocheir japonica larvae were fairly numerous. Larvae of the pea crabs Pinnixa rathbuni and Tritodynamia rathbunae and zoeae of the bigtooth rock crab Glebocarcinus amphioetus were predominant in Ussuriysky Bay.

Impact Assessments of Transgenic cry1Ab Rice on the Population Dynamics of Five Non-Target Thrips Species and Their General Predatory Flower Bug in Bt and Non-Bt Rice Fields Using Color Sticky Card Traps

A 2-yr field study was conducted to assess the effects of transgenic japonica rice (KMD1 and KMD2) with a synthetic cry1Ab gene from Bacillus thuingiensis Berliner on population dynamics and seasonal average densities of five thrips species including Stenchaetothrips biformis (Bagnall), Frankliniella intonsa (Trybom), F. tenuicornis (Uzel), Haplothrips aculeatus (Fabricius), Haplothrips tritici (Kurd) and their general predatory flower bug, Orius similis Zheng as compared to the parental control rice line using the white, blue and yellow sticky card traps. Population dynamics and seasonal average densities of these five thrips species and their general predatory flower bug were not significantly affected by rice type. Additionally, the white sticky card trap was suggested to be the most suitable for monitoring the population of these five thrips species and their general predator. These results show that our tested Bt rice lines do not interrupt the population of non-target thrips species and their general predatory flower bug in the field, and also cannot result in more occurrence of these thrips species in the rice ecosystem.

Impact of afforestation density on soil and water conservation of the semiarid Loess Plateau, China

On the Loess Plateau of China, deep rooted, fast-growing species, such as caragana (Caragana korshinskii Kom.), are widely used in afforestation projects. High planting densities and soil water consumption has led to soil desiccation and degradation. We conducted a two-year (2002 to 2003) field experiment assessing the effect of caragana planting density on plant growth and hydrological processes at the Shanghuang Eco-Experimental station. Caragana canopy interception, surface runoff, soil loss, and changes in plant growth and soil water content were determined for five planting densities ranging from 16 to 87 shrubs 100 m−2 (1,076 ft−2). Increases in the caragana canopy within the growing season and greater planting densities resulted in higher canopy interception and in lower runoff and soil loss. The soil water carrying capacity for the caragana amounted to 72 shrubs100 m−2 when rainfall approaches the long-term average. A sustainable, managed planting density is required that will balance soil water losses due to runoff, the plant9s water requirements, and the water supply. In cases where soil desiccation has already occurred, conservation management plans should attempt to recharge the soil water in order to reverse soil degradation.

Marine mammal acoustic detections in the northeastern Chukchi Sea, September 2007–July 2011

Several cetacean and pinniped species use the northeastern Chukchi Sea as seasonal or year-round habitat. This area has experienced pronounced reduction in the extent of summer sea ice over the last decade, as well as increased anthropogenic activity, particularly in the form of oil and gas exploration. The effects of these changes on marine mammal species are presently unknown. Autonomous passive acoustic recorders were deployed over a wide area of the northeastern Chukchi Sea off the coast of Alaska from Cape Lisburne to Barrow, at distances from 8km to 200km from shore: up to 44 each summer and up to 8 each winter. Acoustic data were acquired at 16kHz continuously during summer and on a duty cycle of 40 or 48min within each 4-h period during winter. Recordings were analyzed manually and using automated detection and classification systems to identify calls.Bowhead (Balaena mysticetus) and beluga (Delphinapterus leucas) whale calls were detected primarily from April through June and from September to December during their migrations between the Bering and Beaufort seas. Summer detections were rare and usually concentrated off Wainwright and Barrow, Alaska. Gray (Eschrichtius robustus) whale calls were detected between July and October, their occurrence decreasing with increasing distance from shore. Fin (Balaenoptera physalus), killer (Orcinus orca), minke (Balaenoptera acutorostrata), and humpback (Megaptera novaeangliae) whales were detected sporadically in summer and early fall. Walrus (Odobenus rosmarus) was the most commonly detected species between June and October, primarily occupying the southern edge of Hanna Shoal and haul-outs near coastal recording stations off Wainwright and Point Lay. Ringed (Pusa hispida) and bearded (Erignathus barbatus) seals occur year-round in the Chukchi Sea. Ringed seal acoustic detections occurred throughout the year but detection numbers were low, likely due to low vocalization rates. Bearded seal acoustic detections peaked in April and May during their breeding season, with much lower detection numbers in July and August, likely as a result of reduced calling rates after breeding season. Ribbon seals (Histriophoca fasciata) were only detected in the fall as they migrated south through the study area toward the Bering Sea. These results suggest a regular presence of marine mammals in the Chukchi Sea year-round, with species-dependent seasonal and spatial density variations.

Spatial and temporal dynamics of Corbicula fluminea (Muller, 1774) in relation to environmental variables in the Mondego Estuary (Portugal)

From 2003 to 2008, research on spatial and temporal dynamics of Corbicula fluminea was conducted at 10 sites along the Mondego Estuary (Portugal). A clear spatial and temporal variation in terms of density and biomass was observed, the highest values being found in the upstream oligohaline site, especially in warmer seasons. Seasonal density ranged from 4 to 11 500 individuals m 22 . Biomass ranged from 0.01 to 323 g ash-free dry weight m 22 . Comparing the results collected in the Mondego Estuary with other European and American invaded ecosystems, the density values are extremely high, but the biomass is lower than some of the reported values. This can be explained by the dominance of very small animals in the Mondego Estuary. Furthermore, the stepwise multiple regression model combining environmental variables and biomass of C. fluminea predicted that the areas with higher values of temperature and phosphate, together with lower values of salinity, water flow and silt and clay, support higher biomass. In 2005, a large reduction in density was recorded and was related to the massive mortality of small individuals as a consequence of the severe drought that occurred in the Mondego Estuary.

Stress-Hormone Levels of Wolves in Relation to Breeding Season, Pack Size, Human Activity, and Prey Density

Human disturbance is thought to be a major source of stress for animals but breeding status, social interactions and food availability are also potential sources. Long-lasting stress may adversely affect the fitness of animals and for that reason the evaluation of stressors is important for conservation of threatened species. The aim of our study was therefore to assess which factors cause stress in wolves (Canis lupus). We evaluated the stress levels of wolves from six packs by measuring the concentration of glucocorticoid metabolites in 59 faecal samples with a Cortisol enzyme-immunoassay. During the breeding season, stress hormone concentration was higher than during the rest of the year, with two peaks around mating and begin of denning, respectively. Multiple regressions ranked by AIC showed that breeding had the highest impact on the wolves' stress levels, followed by human activity, pack size, and prey density. We conclude that human activity is only one of several factors contributing to stress in wolves and that intraspecific competition during breeding is likely to cause elevated levels of glucocorticoids.

Effect of season and stocking density during transport on carcass and meat quality of suckling lambs

Many factors related to transport to abattoir affects meat quality, but scarce information is available in suckling lambs. Thus, the aim of this work was to evaluate the effects of season and stocking density on carcass and meat quality of suckling lambs during commercial transport to the abattoir. A factorial design (2 × 3) was used: two seasons (winter and summer) and three stocking densities (SD; 0.08, 0.12 and 0.20 m2 animal-1). Meat quality variables were measured in the M. longissimus at 24 h post-mortem and after 5 days of refrigerated storage. Lambs transported in summer showed lower liver weight (p<0.001), h* (p<0.05), deoxymyoglobin content (p<0.001), pressed juice (p<0.01), shear force (p<0.001) and firmness (p<0.001), and higher initial pH (p<0.001), L*, b*, C* (p<0.001) and a* (p<0.01), as well as metmyoglobin and oxymyoglobin content (p<0.001), than those transported in winter. The effect of season was dependent on storage time, being colour changes more evident at 24 h than after 5 days of storage, whereas lipid oxidation was only observed in stored meat, which may be explain because the natural antioxidative system decreases with time after slaughter. Scarce effect of SD was found on the carcass and meat quality parameters, thus under our experimental conditions the three SD studied appear to be suitable for suckling lambs transport. However, both carcass and meat quality were within the normal commercial range.

Influence of cambial age and climate on ring width and wood density in Pinus radiata families

The correlation between tree ring width and density and short-term climate fluctuations may be a useful tool for predicting response of wood formation process to long-term climate change. This study examined these correlations for different radiata pine genotypes and aimed at detecting potential genotype by climate interactions. Four data sets comprising ring width and density of half- and full-sib radiata pine families were used. Correlations with climate variables were examined, after the extraction of the effect of cambial age. Cambial age explained the highest proportion of the ring to ring variation in all variables. Calendar year and year by family interaction explained a smaller but significant proportion of the variation. Rainfall had a positive correlation with ring width and, depending on test site, either a negative or positive correlation with ring density. Correlations between temperature during growing season and ring density were generally negative. Climate variables that influence ring width and wood density can be identified from ring profiles, after removing the cambial age effect. Families can be selected that consistently show desirable response to climate features expected to become prevalent as a result of climate change.

Seasonal density and distribution of Octopus tehuelchus in the intertidal of North Patagonia

The abundance and distribution of coastal cephalopods are strongly influenced by the environmental conditions. This study evaluates the seasonal distribution and density of Octopus tehuelchus in three intertidal environments of San Matías Gulf (Patagonia). To estimate and compare density and distribution, monthly transects were carried out, and analysed in relation to the coastlines obtained with satellite images. Densities of O. tehuelchus ranged between 0 and 34 individuals per transect (0–0.11 octopus m−2), and varied between sites. Islote Lobos (IL) had the highest densities (mean octopus per transect 7.32 ± 1.16) followed by El Fuerte (EF) (5.55 ± 0.94) and San Antonio Bay (SAB) (3.40 ± 0.85). Within each site, octopus densities varied between seasons. The highest densities were observed during warm months (SAB = 5.96, EF = 9.52, IL = 14.15) and the lowest during cold ones (SAB = 1.45, EF = 2.6, IL = 3.32). Octopus tehuelchus showed an aggregated spatial distribution, and the nearest neighbour value varied between 0.21 and 0.83 in SAB, 0.27 and 0.78 in EF and 0.23 and 0.53 in IL. Considering the coast lines, the distribution pattern along the intertidal varied seasonally. During warm months this species is widely distributed throughout the intertidal, from the low-tide line to 300 m (in SAB), 500 m (in EL) and 200 m (in IL). On the contrary, during cold months most individuals were found near the low-tide line. These results may be associated with the availability of shelter in the intertidal and the activity and physiology of this species.

Spatial and temporal variability in seasonal snow density

Summary Snow density is a fundamental physical property of snowpacks used in many aspects of snow research. As an integral component in the remote sensing of snow water equivalent and parameterisation of snow models, snow density may be used to describe many important features of snowpack behaviour. The present study draws on a significant dataset of snow density and climate observations from the United States, Australia and the former Soviet Union and uses regression-based techniques to identify the dominant climatological drivers for snow densification rates, characterise densification rate variability and estimate spring snow densities from more readily available climate data. Total winter precipitation was shown to be the most prominent driver of snow densification rates, with mean air temperature and melt-refreeze events also found to be locally significant. Densification rate variance is very high at Australian sites, very low throughout the former Soviet Union and between these extremes throughout much of the US. Spring snow densities were estimated using a statistical model with climate variable inputs and best results were achieved when snow types were treated differently. Given the importance of snow density information in many snow-related research disciplines, this work has implications for current methods of converting snow depths to snow water equivalent, the representation of snow dynamics in snow models and remote sensing applications globally.

Impact of Six TransgenicBacillus thuringiensisRice Lines on Four Nontarget Thrips Species Attacking Rice Panicles in the Paddy Field

As a key component of ecological risk assessments, nontarget effects of Bacillus thuringiensis (Bt) rice have been tested under laboratory and field conditions for various organisms. A 2-yr field experiment was conducted to observe the nontarget effects of six transgenic rice lines (expressing the Cry1Ab or fused protein of Cry1Ab and Cry1Ac) on four nontarget thrips species including Frankliniella intonsa (Trybom), F. tenuicornis (Uzel), Haplothrips aculeatus (F.), and H. tritici (Kurd), as compared with their rice parental control lines. Two sampling methods including the beat plate and plastic bag method were used to monitor the population densities of the four thrips species for 2 yr. The results showed that the seasonal average densities of four tested thrips species in Bt rice plots were significantly lower than or very similar to those in the non-Bt rice plots depending on rice genotypes, sampling methods, and years. Among all six tested Bt rice lines, transgenic B1 and KMD2 lines suppressed the population of these tested thrips species the most. Our results indicate that the tested Bt rice lines are unlikely to result in high population pressure of thrips species in comparison with non-Bt rice. In some cases, Bt rice lines could significantly suppress thrips populations in the rice ecosystem. In addition, compatibility of Bt rice, with rice host plant resistance to nontarget sucking pests is also discussed within an overall integrated pest management program for rice.

Ecological and demographic correlates of helping behaviour in a cooperatively breeding bird

The evolution of cooperation is a persistent problem for evolutionary biologists. In particular, understanding of the factors that promote the expression of helping behaviour in cooperatively breeding species remains weak, presumably because of the diverse nature of ecological and demographic drivers that promote sociality. In this study, we use data from a long-term study of a facultative cooperative breeder, the long-tailed tit Aegithalos caudatus, to investigate the factors influencing annual variation in helping behaviour. Long-tailed tits exhibit redirected helping in which failed breeders may become helpers, usually at a relative's nest; thus, helping is hypothesised to be associated with causes of nest failure and opportunities to renest or help. We tested predictions regarding the relationship between annual measures of cooperative behaviour and four explanatory variables: nest predation rate, length of the breeding season, population-level relatedness and population density. We found that the degree of helping was determined principally by two factors that constrain successful independent reproduction. First, as predicted, cooperative behaviour peaked at intermediate levels of nest predation, when there are both failed breeders (i.e. potential helpers) and active nests (i.e. potential recipients) available. Second, there were more helpers in shorter breeding seasons when opportunities for renesting by failed breeders are more limited. These are novel drivers of helping behaviour in avian cooperative breeding systems, and this study illustrates the difficulty of identifying common ecological or demographic factors underlying the evolution of such systems.

Seasonal nekton assemblages in a flooded coastal freshwater marsh, Southwest Louisiana, USA

Marsh flooding and drying may be key factors affecting seasonal nekton distribution and density because habitat connectivity and water depth can impact nekton accessibility to the marsh surface. Recent studies have characterized freshwater nekton assemblages in marsh ponds; however, a paucity of information exists on the nekton assemblages in freshwater emergent marshes. The principal objectives of this study are to characterize the seasonal nekton assemblage in a freshwater emergent marsh and compare nekton species composition, density, and biomass to that of freshwater marsh ponds. We hypothesize that 1) freshwater emergent marsh has lower taxa richness than freshwater marsh ponds; and 2) freshwater emergent marsh has a lower seasonal density and biomass than freshwater marsh ponds. Mosquitofish Gambusia affinis and least killifish Heterandria formosa were abundant species in both habitats while some abundant species (e.g., banded pygmy sunfish Elassoma zonatum) in freshwater ponds were absent in freshwater emergent marsh. Our data did not support our first and second hypotheses because taxa richness, seasonal density and biomass between freshwater emergent marsh and ponds did not statistically differ. However, freshwater emergent marsh was dry during the summer months and thus supports no fish species during this period. Additional long-term research on the effects of flow regime in the freshwater marsh on nekton assemblages would potentially improve our understanding of nekton habitat requirements.

Seasonal comparison of aquatic macroinvertebrate assemblages in a flooded coastal freshwater marsh

Marsh flooding and drying may be important factors affecting aquatic macroinvertebrate density and distribution in coastal freshwater marshes. Limited availability of water as a result of drying in emergent marsh may decrease density, taxonomic diversity, and taxa richness. The principal objectives of this study are to characterize the seasonal aquatic macroinvertebrate assemblage in a freshwater emergent marsh and compare aquatic macroinvertebrate species composition, density, and taxonomic diversity to that of freshwater marsh ponds. We hypothesize that 1) freshwater emergent marsh has lower seasonal density and taxonomic diversity compared to that of freshwater marsh ponds; and 2) freshwater emergent marsh has lower taxa richness than freshwater marsh ponds. Seasonal aquatic macroinvertebrate density in freshwater emergent marsh ranged from 0 organisms/m2 (summer 2009) to 91.1 ± 20.53 organisms/m2 (mean ± SE; spring 2009). Density in spring was higher than in all other seasons. Taxonomic diversity did not differ and there were no unique species in the freshwater emergent marsh. Our data only partially support our first hypothesis as aquatic macroinvertebrate density and taxonomic diversity between freshwater emergent marsh and ponds did not differ in spring, fall, and winter but ponds supported higher macroinvertebrate densities than freshwater emergent marsh during summer. However, our data did not support our second hypothesis as taxa richness between freshwater emergent marsh and ponds did not statistically differ.

Constraining annual and seasonal radon-222 flux density from the Southern Ocean using radon-222 concentrations in the boundary layer at Cape Grim

ABSTRACTRadon concentrations measured between 2001 and 2008 in marine air at Cape Grim, a baseline site in north-western Tasmania, are used to constrain the radon flux density from the Southern Ocean. A method is described for selecting hourly radon concentrations that are least perturbed by land emissions and dilution by the free troposphere. The distribution of subsequent radon flux density estimates is representative of a large area of the Southern Ocean, an important fetch region for Southern Hemisphere climate and air pollution studies. The annual mean flux density (0.27 mBq m−2 s−1) compares well with the mean of the limited number of spot measurements previously conducted in the Southern Ocean (0.24 mBq m−2 s−1), and to some spot measurements made in other oceanic regions. However, a number of spot measurements in other oceanic regions, as well as most oceanic radon flux density values assumed for modelling studies and intercomparisons, are considerably lower than the mean reported here. The reported radon flux varies with seasons and, in summer, with latitude. It also shows a quadratic dependence on wind speed and significant wave height, as postulated and measured by others, which seems to support our assumption that the selected least perturbed radon concentrations were in equilibrium with the oceanic radon source. By comparing the least perturbed radon observations in 2002–2003 with corresponding ‘TransCom’ model intercomparison results, the best agreement is found when assuming a normally distributed radon flux density with σ=0.075 mBq m−2 s−1.

Ecological gradients and landscape structure affecting seasonal woodpigeon Columba palumbus densities in a coastal region (South- East Spain)

Gradients écologiques et structure du paysage affectant les densités saisonnières du Pigeon ramier Columba palumbus en zone côtière dans le Sud-Est de l’Espagne. Le but de cet étude est d’identifier et d’évaluer le lien entre la densité de Pigeon ramier (Columba palumbus, Linnaeus, 1758) et différents gradients environnementaux, l’occupation du sol et la structure du paysage, en utilisant des outils issus des systèmes d’information géographiques et de la modélisation multivariée. Des transects (n = 396) ont été développés pour estimer la densité du Pigeon ramier dans la région de Marina Baja (Alicante, Espagne) de 2006 à 2008. C’est en septembre-octobre que la densité de Pigeons ramiers était la plus élevée (1,28 oiseaux/ 10 ha) et en février-mars qu’elle était la plus basse (0,34 oiseaux/ 10 ha). En outre, il y avait plus de Pigeons ramiers dans les zones avec un thermotype mésoméditerranéen que dans celles de types thermoméditerranéen ou supraméditerranéen. Les densités les plus élevées ont été observées dans des zones intermédiaires par rapport à la côte et à l’arrière-pays. C’est dans une matrice paysagère naturelle, caractérisée par des densités variables de pins, qu’ont été observées les densités les plus fortes de l’espèce (1,53 individus/ 10 ha). Par conséquent, il est très important de conserver ces paysages traditionnels avec les stratégies de gestion adéquates afin de maintenir les populations de cette palombe. Ces espaces naturels sont des lieux semi-ouverts où les pigeons trouvent de la nourriture et peuvent surveiller la présence de prédateurs. Ainsi, cette étude permettra une connaissance plus précise des facteurs écologiques qui interviennent dans la répartition du Pigeon ramier en zone méditerranéenne.

Seasonal composition and population density of zooplankton in Lake Karaboğaz from the Kızılırmak Delta (Samsun, Turkey)

Zooplankton composition and abundance were investigated seasonally at 6 sites in Lake Karabogaz in relation to some physicochemical conditions. A total of 63 taxa were identified, among them 51 species of rotifers, 8 cladocerans, and 4 copepods. Rotifera represented the predominant component (79% of the total community), followed by nauplii, cladocerans, and copepods (15%, 5%, and 1%, respectively). The average total zooplankton abundance ranged from 9603 to 22,968 ind/m3. The maximum and the minimum densities were measured in June and August of 2009, respectively. Of the identified zooplankton, 39 taxa were species with a low frequency in the lake. Among the species with the highest frequency of encounter were Coronatella rectangula, Chydorus sphaericus, Colurella adriatica, Keratella quadrata, Lecane closterocerca, L. bulla, and Polyarthra vulgaris. Zooplankton diversity showed a positive correlation with temperature and chlorophyll a. However, a significant negative correlation was detected between diversity and salinity.