Seasonal Variation In Abundance Research Articles

Spatial and temporal patterns of benthic polychaete communities on the northern Gulf of Mexico continental slope

Community structure and abundance of benthic polychaetes along a transect on the central northern Gulf of Mexico continental slope were examined. Spatial, seasonal, short- (~1 year), and long-term (~16–17 years) temporal comparisons of assemblages were conducted with samples collected in 1983–1984 and 2000–2001. Polychaete abundance did not consistently decrease between 325 and 1500 m, but sharply decreased between 1500 and 2100 m. On the upper slope (325–1500 m) polychaete abundance approximately doubled between fall 1983 and spring 1984, but had returned to initial levels by fall 1984. On the lower slope (2500 m) seasonal variations in abundance were less pronounced. The taxonomic composition of the polychaete assemblages changed continuously along a depth gradient; however, temporal variations of the assemblages at all water depths were generally minor. This study provides a baseline for naturally occurring spatial and temporal dynamics of benthic polychaete communities on the northern Gulf of Mexico continental slope.

Composition and seasonal variations in abundance of Copepod (Crustacea) populations from the northern part of Lake Tanganyika

Copepod has an important ecological role as a main food of several fishes on which commercial fisheries are based in Lake Tanganyika. However, very little multi-annual monitoring programs have been conducted for this group of crustacean zooplankton. This study was conducted in the northern part of Lake Tanganyika by weekly sampling at both pelagic and littoral sites over three consecutive years (2012–2014). The analyzed samples showed that Lake Tanganyika copepod was essentially composed of three suborders including Calanoida (30% by number) with a single endemic species, Cyclopoida (69%) with four dominant species and Harpacticoida (1%). These taxa showed variations in their abundance respectively at pelagic and littoral sampling sites. The average densities of copepods did slightly vary during the sampling period in both areas although higher peaks were observed in 2013. For the post-nauplii stage, Tropocyclops tenellus predominated while the nauplii of T. simplex predominated at both sampling sites. Seasonal fluctuations of copepod densities showed higher peaks in September/October and April/May, respectively, for the three most common species. T. simplex and M. aequatorialis ovigerous females showed higher peaks in the rainy season in 2013. These results can benefit pelagic fisheries research and lake environmental management efforts as the copepod abundance seems to be closely correlated to that of sardines in Lake Tanganyika.

Records of the Cave-Dwelling Bats (Mammalia: Chiroptera) of Hispaniola with an Examination of Seasonal Variation in Diversity

Despite a long history of scientific collection of bats, Hispaniola remains the least studied island of the Greater Antilles. Using standardized trapping methods during the wet and dry season at four major caves — Honda de Julian, La Chepa, Los Patos, and Pomier #4, we sampled a total of 1,472 individuals in four families, 11 genera and 12 species (of 18 recorded for the island). We report significantly fewer captures on the second night of sampling. We document seasonal variation in abundance of Macrotus waterhousii, Monophyllus redmani, and Artibeus jamaicensis, that results in 1–4 more species captured in the wet season. Additionally, singleton captures at all caves except for Honda de Julian produced wide confidence intervals in estimates of richness. Finally, we highlight the role of caves as major ecosystems for maintaining Hispaniolan mammal biodiversity. The high diversity recorded at La Chepa, together with possible declines at the historically very diverse Los Patos, highlight the conservation i...

Seasonal Variation of Harbor Seal's Diet from the Wadden Sea in Relation to Prey Availability.

The Wadden Sea has an important role for marine mammals in terms of resting, nursing and foraging. Harbor seal is the most abundant marine mammal species in this area. The use of the food resources of the Wadden Sea by seals is not clear, and previous studies showed that this species can travel kilometers away from their haul-outs to forage in the North Sea. In this study, we analyzed the stable isotopes of vibrissae from 23 dead harbor seals found on the island of Sylt to investigate their diet. The predator´s carbon and nitrogen isotope compositions were compared to the compositions of different potential prey items from the Sylt-Rømø Bight and from the North Sea in order to study seasonal pattern in the diet and in the foraging location. In parallel, seasonal variation of abundance and biomass of the potential prey items from the Sylt-Rømø Bight were studied and compare to their contribution to the seal´s diet. The results revealed a change in the seal´s diet from pelagic sources in spring to a benthic based diet in summer, and an increasing use of the North Sea resources in fall and winter in accordance with the seasonal variation of the availability of prey in the Sylt-Rømø Bight.

English

Aflatoxin contamination impinges on grain quality worldwide. The causative agent, Aspergillus spp. colonizes grain in the field down to postharvest stages in storage where they may produce toxins. Kenya has experienced recurring cases of aflatoxicosis in Eastern region especially during periods of maize grain deficit. The risk of chronic exposure has not been widely studied. Therefore, seasonal variation in abundance and species composition of toxigenic Aspergillus in maize and soils of Eastern Kenya was investigated. Samples were obtained from farmers, two months after the first (May) and second (December) harvest seasons. Aspergillus spp. were isolated from maize and soil samples by direct and dilution plate techniques respectively on Czapek Dox Agar (CZ) and thereafter sub-cultured on potato dextrose agar (PDA). Positive identification was done using culture-morphological and microscopic characteristics in PDA media. The ammonium vapour test was used to screen for the putative toxigenic strains. A total of 229 Aspergillus spp. cultures were obtained (55% -maize, 45% -soil). Eleven Aspergillus sp. were identified: Aspergillus niger, Aspergillus flavus, Aspergillus clavatus, Aspergillus awamori, Aspergillus parasiticus, Aspergillus ochraceus, Aspergillus candidus, Aspergillus ustus, Aspergillus niveus, Aspergillus terreus and Aspergillus wentii. Of these 41 (18 %) were potentially toxigenic while the rest were putatively atoxigenic. Out of the 41 toxigenic isolates, 22 were from maize. The first season had 15 (68.2%) toxigenic maize isolates while 7 (31.8%) were from the second season. Generally, there were more fungal isolates in the first season (54.1%) than the second one (45.9%) while Aspergillus niger was the most abundant in both seasons. Such variation in fungal abundance supports the hypothesis that aflatoxin contamination of grain may vary seasonally but that remains to be unravelled and herein, a contrary opinion was presented. Key words: Aflatoxin, mycotoxin, Aspergillus, maize, soil.

Risso's Dolphin, Grampus griseus, in the Western Ligurian Sea: Trends in Population Size and Habitat Use.

This paper provides a summary of 25 years of research on Risso's dolphins (Grampus griseus) in the western Ligurian Sea. Seasonal variations in abundance, distribution and habitat use were observed. Photographic mark-recapture methods provided a population size estimate for the period from 1998 to 2012, of about 100 individuals (95% CI of 60-220 individuals). The same methods detected a decline in population size from an average of about 120-150 from 2000 to 2005, to an average of 70-100 during 2010 to 2014. Species occurrence appeared to be significantly decreasing in coastal and continental slope areas, while it seemed to be stable in the most pelagic area. In addition, a dramatic change was observed in the local primary production, which was analysed based on time series of sea surface temperature and chlorophyll data from 1990 to 2014. Based on fisheries landings, there may have been a general decrease in fishery productivity, both in the western Ligurian Sea and in adjacent regions. Environmental variability, depletion of resources by fisheries and possibly interspecies competition may all have contributed to cause changes in Risso's dolphin habitat use and occurrence in the western Ligurian Sea.

Seasonal variations in abundance and diversity of insect pollinator in forest ecosystems of Southern Punjab Pakistan

Seasonal variations in abundance and diversity of insect pollinator in forest ecosystems of Southern Punjab Pakistan

Seasonal variation in abundance and species composition of the Parmales community in the Oyashio region, western North Pacific

Seasonal variation in abundance and species composition of the Parmales community in the Oyashio region, western North Pacific

Mark‐resight estimates of seasonal variation in harbor seal abundance and site fidelity

AbstractMonitoring trends in abundance of pinnipeds typically involves counting seals at terrestrial haul‐out sites during the breeding season. Counts of seals made at other times of the year are typically lower; however, it is often unknown whether this is because fewer animals are present or whether lower counts simply reflect a reduction in haul‐out probability. Here we illustrate how photo‐identification data from an individual‐based study of harbor seals (Phoca vitulina) can be used to estimate seasonal variation in abundance and site fidelity. Monthly data collected over a two‐year period were analyzed using a mark‐recapture mark‐resight model accounting for individuals transitioning between observable and unobservable states. Levels of site fidelity were high throughout the year and abundance estimates showed no seasonal pattern. This suggests that individual seals used haul‐out sites to the same extent throughout the year, and that peaks in counts during the breeding season are a result of seasonal changes in haul‐out probability. The results of this study have implications for understanding population sub‐structuring, gene flow and disease spread.

Arthropods Associated with Carrion in a Salt Marsh Habitat in Southeastern Florida

Abstract Few studies have assessed arthropods associated with carrion in salt marsh environments. Arthropods attracted to animal carcasses in a salt marsh environment were surveyed in southeastern Florida during four seasons from September 2009 to July 2010. A total of 2,324 arthropod specimens were collected from carcasses (coyote, opossum, raccoon, bobcat, and otter) and 4 orders, 23 families, 28 genera, and 24 species were identified. Specimens were most frequently encountered from the order Diptera (85% of total), and Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) and Musca domestica (L.) (Diptera: Muscidae) represented 50% of specimens collected. We observed seasonal variation in abundance of dipterans. The information presented here may be useful for future studies identifying arthropods having wildlife forensic entomology significance within subtropical Florida salt marsh habitats.

Seasonal variations in abundance, biomass and grazing rates of microzooplankton in a tropical monsoonal estuary

Seasonal abundance, composition and grazing rates of microzooplankton (20–200 µm) in the Zuari estuary were investigated to evaluate their importance in food web dynamics of a tropical monsoonal estuary. Average abundances of microzooplankton (organisms × 104 l−1) during the three seasons were 0.44 (southwest monsoon), 1.13 (post-monsoon) and 0.96 (pre-monsoon). Protozoan (ciliates, heterotrophic dinoflagellates and sarcodines) accounted for most (96 %) of the microzooplankton community, with micrometazoan (nauplii and copepodid stages of copepods, fish eggs, etc.). being far less abundant. Among protozoans, ciliates (loricates and aloricates) were most numerous (69 % of the total microzooplankton). Statistically significant (p 60 %) by the pico and nano fraction (<20 µm) for most of the year. Phytoplankton growth rates (day−1) ranged between 0.69 and 1.24. Microzooplankton grazing was estimated to consume 30–82 % of the phytoplankton standing stock, and 58–97 % of the daily primary production. Results of the present study highlight the role of the microzooplankton as an important consumer of phytoplankton production.

Description, molecular phylogeny, and natural history of a new kleptoparasitic species of gelechiid moth (Lepidoptera) associated with Melastomataceae galls in Brazil

The male, female, pupa and larva of a new species of Gelechiidae (Lepidoptera), Locharcha opportuna Moreira and Becker, are described and illustrated with the aid of optical and scanning electron microscopy. A preliminary analysis of mitochondrial DNA sequences including members of related lineages is also provided. The immature stages are associated with galls induced by a species of Palaeomystella Fletcher (Lepidoptera: Momphidae) on Tibouchina sellowiana (Cham.) Cogn. (Melastomataceae), endemic to the Atlantic Rainforest. Larvae are kleptoparasitic, usurping the gall internal space and thereafter feeding on the internal tissues. By determining the variation in population density of both species and following gall development individually throughout ontogeny under field conditions, we demonstrated that the kleptoparasite completes its life cycle inside galls induced by Palaeomystella, where pupation occurs. The variation in seasonal abundance of the kleptoparasite is tied to that of the cecidogenous species, with their corresponding peaks in density occurring sequentially.http://zoobank.org/urn:lsid:zoobank.org:pub:525F6D52-8CE1-47D1-A0D9-78B564DF5565

What cortisol can tell us about the costs of sociality and reproduction among free-ranging rhesus macaque females on Cayo Santiago.

Research with the rhesus macaque population on Cayo Santiago can provide a unique perspective on the costs of sociality and reproduction in primates. Because the Cayo macaques live in unusually large groups and in a predator-free environment, in which their artificial food source lacks seasonal variation in abundance or quality, these monkeys constitute a semi-experimental study of the costs and benefits of group living. Here we review several long- and short-term studies that have focused on female life history and stress physiology. Long-term demographic data have shown that rhesus macaque females of middle- and low-ranking matrilines have lower adult survival probabilities than females of high-ranking matrilines. Costs of reproductive effort are also evident: adult females were more likely to die during the birth than during the mating season and they experienced higher cortisol levels when lactating. Lower-ranking females, in particular, experienced greater relative increase in cortisol production during lactation, in comparison to middle- and high-ranking females. Older high-ranking females had lower plasma cortisol levels than younger ones but cortisol levels were similarly high among young and old middle- and low-ranking females. Higher plasma cortisol levels and/or fecal glucocorticoid concentrations are associated with higher plasma concentrations of some proinflammatory cytokines. High cortisol, in turn, may be associated with chronic inflammation, and perhaps also with immunosuppression. In sum, the studies reviewed here provide multiple lines of evidence that sociality and reproductive effort impose measurable costs on female rhesus macaques. In line with socio-ecological theory, female dominance rank consistently emerges as an important modulator of variation in female life histories and physiology. The Cayo Santiago macaques are therefore a valuable model for elucidating the mechanisms by which within-group competition and reproduction impact health and survival in nonhuman primates and in humans.

Evaluation of seasonal variations in abundance of BTXE hydrocarbons and their ozone forming potential in ambient urban atmosphere of Dehradun (India)

In Dehradun, ambient volatile organic compounds (VOC) samples were collected for three seasons viz. summer, winter and monsoon (during period 2012–2013) to investigate seasonal variations at five different sampling sites. The samples were quantified for aromatic VOCs by gas chromatography (GC-FID) to monitor benzene, toluene, m, p-xylene, o-xylene and ethylbenzene. BTXE comprise an important group of VOCs mostly prevalent in a typical urban environment. They were monitored because they are known to cause impacts on climate, health and on vegetation. Toluene was found to be the most abundant VOC among the measured ones in the atmosphere of Dehradun. The maximum mean concentration of VOCs was observed in winters and lowest during summers for BE species. Toluene ambient concentration was rather found to register highest during winters and lowest in monsoons. Kruskal–Wallis test showed statistically significant differences seasonally (p 1) observed ratio indicates vehicular emission as their major source. BTEX were also evaluated for their ozone-forming potential (OFP). Toluene and xylenes were found as the highest contributing hydrocarbons towards ozone forming potential among BTXE.

Distribution of hard tick species in Ankara, Turkey

A systematic study has been carried out on hard ticks from Ankara Province, Turkey. Between April 2010 and July 2012, 1800 tick specimens belonging to 9 species were identified at 31 locations in 9 districts. Tick species are listed as follows: Rhipicephalus sanguineus group (43.44%), Rhipicephalus bursa (36.67%), Hyalomma marginatum (8.83%), Haemaphysalis parva (6%), Hyalomma aegyptium (2.39%), Hyalomma excavatum (1.33%), Dermacentor marginatus (1.06%), Haemaphysalis punctata (0.22%), and Hyalomma detritum (0.06%). Ticks were collected from host animals and from vegetation via the flagging method. The species of the genus Rhipicephalus were present in most of the study areas, the most common being the Rhipicephalus sanguineus group (20/31). Hyalomma species were mostly collected from host animals, with Hyalomma marginatum being the most common species in this genus (8.83%). We also observed seasonal variations in abundance, with the highest number in May. The district with the most abundant ticks was determined to be Kizilcahamam, which had the highest tick abundance rate of 28.6%.

Seasonal variations of abundance and live/dead compositions of copepods inMersin Bay, northeastern Levantine Sea (eastern Mediterranean)

The seasonality of abundance and live/dead compositions of copepods was studied in the northeastern Mediterranean Sea. Zooplankton, chlorophyll-a, and PO4 sampling was performed on a monthly basis from March 2006 to February 2007 at both a coastal station and an open water station. At the coastal station, high phytoplankton biomass was driven by PO4 input from the Lamas River. On annual average, copepod abundance was 53,075 and 140,227 ind. m-2 at the coastal and open water stations, respectively. The most common copepod taxa were Oithona similis, Euterpina acutifrons, Labidocera spp., Oncaea media, and Temora spp. at the coastal station, and Oncaea media, Labidocera spp., Lucicutia spp., Farranula spp., Oithona similis, and Microsetella spp. at the open water station. At the coastal station, dead copepods did not exceed 7% of the population; on annual average, 2.6% of the copepods were dead. At the open water station, on average 10.6% of the copepod population appeared dead; the percentages of dead copepods reached 29.5% in April and 21.7% in May 2006, suggesting that the copepod community suffered higher nonpredatory mortality at the open water station than at the coastal station, especially in the spring.

Bacterial diversity in the South Adriatic Sea during a strong, deep winter convection year.

The South Adriatic Sea is the deepest part of the Adriatic Sea and represents a key area for both the Adriatic Sea and the deep eastern Mediterranean. It has a role in dense water formation for the eastern Mediterranean deep circulation cell, and it represents an entry point for water masses originating from the Ionian Sea. The biodiversity and seasonality of bacterial picoplankton before, during, and after deep winter convection in the oligotrophic South Adriatic waters were assessed by combining comparative 16S rRNA sequence analysis and catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). The picoplankton communities reached their maximum abundance in the spring euphotic zone when the maximum value of the chlorophyll a in response to deep winter convection was recorded. The communities were dominated by Bacteria, while Archaea were a minor constituent. A seasonality of bacterial richness and diversity was observed, with minimum values occurring during the winter convection and spring postconvection periods and maximum values occurring under summer stratified conditions. The SAR11 clade was the main constituent of the bacterial communities and reached the maximum abundance in the euphotic zone in spring after the convection episode. Cyanobacteria were the second most abundant group, and their abundance strongly depended on the convection event, when minimal cyanobacterial abundance was observed. In spring and autumn, the euphotic zone was characterized by Bacteroidetes and Gammaproteobacteria. Bacteroidetes clades NS2b, NS4, and NS5 and the gammaproteobacterial SAR86 clade were detected to co-occur with phytoplankton blooms. The SAR324, SAR202, and SAR406 clades were present in the deep layer, exhibiting different seasonal variations in abundance. Overall, our data demonstrate that the abundances of particular bacterial clades and the overall bacterial richness and diversity are greatly impacted by strong winter convection.

Core and transient species in an Amazonian savanna bird assemblage

In this paper, we report the number of core and transient bird species in an Amazonian savanna site and assess their ecological differences. We conducted our study at Campo Experimental do Cerrado (CEC) da Embrapa–Amapa, 48 km north of Macapa (0 2'5 N / 51 2'2 W), Amapa, Brazil. Forty points were monitored on a monthly basis over the course of one year, using the unlimited-distance point counts in a plot of 360 hectares of well-preserved and relatively homogeneous upland savanna from September 2006 to August 2007. Species were classified in core (recorded in the area in nine or more months), transient (recorded in the area in four or less months) and intermediate (the ones recorded between five and eight months). Species were also classified according to feeding guilds and habitat preferences. Statistical analyses were made to compare core and transient species. We recorded 72 species in the plot, of which 36 were transients, 12 were intermediates, and 22 were core. Core species have higher abundances than transient species. Core species are found mostly in the savanna while transient species also occur in other habitats within the landscape. Both core and transient groups presented well-marked seasonal variation in abundance. Recruitment explains abundance variation for core species, while differences in the availability of food resources in the site explains variation of the abundance in transient species. We predict that plot-level (not more than 500 hectares) bird assemblages in South American savannas will be composed of a small number of abundant and habitat-restricted species that occupy the site almost year round, combined with a high number of low abundant transient species that are habitat generalists and use the plot only during limited periods of their annual life cycle.

First report of the presence of Acartiabispinosa Carl, 1907 (Copepoda, Calanoida) in a semi-enclosed Bay (Sharm El-Maya), northern Red Sea with some notes on its seasonal variation in abundance and body size.

The calanoid copepod, Acartia bispinosa Carl, 1907, is reported for the first time in the Red Sea, where it is found to be an important copepod in the mesozooplankton community structure of the Sharm El-Maya Bay. Female and male are fully redescribed and illustrated of as the mouthparts of this species have never previously been described and figured. Acartia bispinosa was collected in the plankton samples throughout the year and showed two peaks of abundance, a pronounced one in April (4234 individuals m-3), and second smaller peak during November (1784 individuals m-3). The average total length of females varied between 1.32 and 1.53 mm at the end of June and January respectively. For males, the average total length fluctuated between 1.07 and 1.16 mm at end of June and March respectively. Temperature showed an inverse relationship with the body length (P > 0.001) and seemed to be one of the prime factors affecting the body length of both sexes.

Species composition and seasonal variation in abundance of Phyllostomidae bats (Chiroptera) in an Atlantic Forest remnant, southeastern Brazil

Normally, the Phyllostomidae bat community var- ies in number of individuals depending on food availability, which in turn varies with changes in annual rainfall. The aims of this study were to list species of Phyllostomidae bats in Curi o Municipal Natural Park located in the munici- pality of Paracambi, state of Rio de Janeiro, southeastern Brazil, and determine possible differences in species rich- ness, abundance and composition between rainy and dry seasons. Sampling was carried out between September 2011 and August 2012 with the use of mist nets. The total sampling effort was 51,840 m 2 h, and 745 individuals of 18 bat species were caught. Myotis riparius (Vespertilionidae) was the only non-Phyllostomidae species caught. Artibeus lituratus and Carollia perspicillata were the most abundant species. The collector curve did not become stabilized, with 21 ± 2 phyllostomid species being estimated for the park. No significant difference in species richness or change in the community composition was found between seasons; how- ever a higher number of individuals was captured in the rainy season. The occurrence of specie indicator of good- quality habitats ( Chrotopterus auritus , Micronycteris micro- tis and Trachops cirrhosus ) and species threatened with extinction ( Chiroderma doriae and Dermanura cinerea ) indicate that the park is an important forest remnant for the conservation of bats and needs to be monitored.