Planktonic Copepod Community Research Articles

Oithona davisae: naturalization in the Black sea, inter-annual and seasonal dynamics, effect on the structure of the planktonic copepod community

Long-term (20032014) routine observations of zooplankton in Sevastopol Bay (the Black Sea) have allowed the naturalization of the invasive copepod Oithona davisae to be studied in the Black Sea coastal waters. Inter-annual and seasonal variability of the species and their impact on the native copepod community have been analyzed. The invasion of O. davisae and their undoubted dominance in terms of abundance were shown to alter the community structure but, at the same time, the abundances of the native species did not decrease, excepting the Black Sea earlier invader Acartia tonsa. A significant decline in A. tonsa numbers over the stages of O. davisae establishment and naturalization provided evidence of competition between the species. O. davisae have been demonstrated to gain competitive advantage over A. tonsa, that ensured their fast dispersal in the Black Sea, acclimatization in the new habitat and the successful competition over native species.

Oithona davisae: Naturalization in the Black Sea, Interannual and Seasonal Dynamics, and Effect on the Structure of the Planktonic Copepod Community

Naturalization of the invasive copepod Oithona davisae is examined based on long-term (2003–2014) routine observations of zooplankton in Sevastopol Bay (the Black Sea). The study analyzes inter-annual and seasonal variability of the species and their impact on the native copepod community. The invasion of O. davisae and their undoubted dominance in terms of abundance have been shown to alter the community structure, while not causing a decline in abundance of native species, except the earlier Black Sea invader Acartia tonsa. A significant decline in A. tonsa numbers over the phases of establishment and naturalization of O. davisae indicates competition between the species. It has been demonstrated that O. davisae have gained a competitive advantage over A. tonsa, which ensured the rapid spread of the former across the Black Sea, acclimatization to the new habitat, and successful competition over native species.

Planktonic copepod community of a reef zone in the southern Gulf of Mexico

ABSTRACTIn this study, the variation of seasonal and inter-annual density and diversity of the copepod community in the Parque Nacional Sistema Arrecifal Veracruzano (PNSAV) was analysed. Samples were collected under nortes, rainy and dry weather conditions in 2011, as well as under nortes and dry weather conditions in 2012 and 2013 in four transects. Surface trawls with 330-μm conical nets were made. The temperature, salinity and dissolved oxygen were measured in situ. The values obtained were 23.07 ± 0.53 to 29.29 ± 0.27°C for temperature, 33.43 ± 0.49 to 35.91 ± 0.09 for salinity, and 2.52 ± 0.08 to 6.56 ± 0.08 mg l−1 for dissolved oxygen. The copepods collected belonged to 19 families, 28 genera and 62 species. Copepods represented between 69.74% and 76.79% of the abundance of crustaceans present in zooplankton. The highest number of copepods occurred under nortes weather conditions in 2011 with 401,885 ± 28,092 copepods/100 m3 of the species Temora stylifera. In 2012, 256,325 ± 76,872 copepods/100 m3 of the species Paracalanus aculeatus were obtained and in 2013, 311,526 ± 76,872 copepods/100 m3 of the species T. turbinata. The highest specific richness was found in the southern zone with 28 species. In 2013 the highest density was found in the northern zone with 100,323 ± 28,888 copepods/100 m3. The highest diversity was found under dry weather conditions in 2011 with 3.71 bits/individual. In the 3 years of study, 24 species were dominant; 12 of these, appeared in the 3 years of sampling: T. stylifera, T. turbinata, Labidocera scotti, P. aculeatus, O. latus, Pontellopsis villosa, Centropages velificatus, Parvocalanus crassirostris, Corycaeus speciosus, Undinula vulgaris, Oithona plumifera, and Farranula gracilis. Canonical correlation analysis showed the formation of five groups explained by the neritic or oceanic affinity of the species and their tolerance to changes in salinity or temperature.

Water quality affects the structure of copepod assemblages along the Sfax southern coast (Tunisia, southern Mediterranean Sea)

The Sfax southern coast (Gulf of Gabes, Mediterranean Sea) has been under increased anthropogenic pressure for many years. In the present study we investigated the effects of this anthropisation on the spatial distribution of copepod assemblages in relation to the physicochemical features of seawater at 20 stations sampled on 19 March 2013. Copepods represented 73% of total zooplankton abundance. Small planktonic copepods (<1.45mm), including pollution-tolerant species (e.g. Oithona nana, Paracalanus parvus, Harpacticus littoralis and Tisbe battagliai), proliferated exclusively in stations of ~0.5-m depth characterised by high coastal anthropogenic inputs. The largest copepod species were dominated by Calanus helgolandicus (1.45–2.5mm) in the offshore zone in depths of ~3m. Substantial numbers of Oithona plumifera (7.5%) were found at depths between 0.5 and 3m. Copepod diversity was significantly higher in the southern zone, which is less affected by sewage, than in the northern zone, which was subjected to higher pressure (Shannon–Wiener index H′=1.5–2.5 and ≤1.5 bits individual–1). A shift in the planktonic copepod community between the two zones was linked to deterioration of water quality, with higher phosphorus levels, turbidity and chemical oxygen demand (COD) in the northern zone.

Long-term changes in copepods assemblages in the area of the Danube floodplain (Slovak–Hungarian stretch)

The present study investigates the relationship between hydrological connectivity and species diversity in a by-passed channel section, and in the adjacent water bodies of the Slovak–Hungarian Danube section (1,840.5–1,804.4 rkm). The study was designed to assess long-term temporal trends (from 1991 to 2013) in freshwater copepods assemblages and their ecological indices in different habitats of the Danube floodplain area. One of the purpose of this study was to monitor the species composition of copepods communities and ascertain their shift in various biotopes of the Danube floodplain system. Based on 23 years data, in the first step, the copepods habitat preferences using habitat values (HV) and indicator weights (IW), calculated from data collected over all the years of monitoring of planktonic communities of the Danube floodplain, were quantified. Subsequently, the floodplain index (FI) from a summary of the habitat values and indication weights of the current species was calculated, to evaluate changes in the connectivity of the anabranched section of the Slovak–Hungarian Danube. This confirmed the loss of active hydrological connectivity within the main river channel, ranging from the eupotamal to more or less isolated floodplain water bodies. Out of 50 recorded copepods species, 11 species manifest a preference for eupotamal habitats, 18 taxa preferred eupotamal B/parapotamal habitats and 21 species were found to prefer the plesiopotamal habitat type. The statistical analyses demonstrated that the structure of planktonic copepod communities in this area has changed since the Gabčíkovo hydropower plant was placed into operations. The NMDS analysis revealed shifts in the proportion of euplanktonic and tychoplanktonic species. Reversible community changes were found in the old river bed and in the eupotamal-B side arms.

Monsoonal changes in the planktonic copepod community structure in a tropical coral-reef at Tioman Island, Malaysia

In order to test the hypothesis that species composition of planktonic copepods varies with seasonal monsoons in tropical coral reef waters of South East Asia, we investigated the copepod community structure in a coral reef of Malaysia over different monsoonal periods (the southwest, the northeast and inter-monsoons). Small copepods such as Paracalanus elegans and Oithona spp. were the predominant taxa, comprising 65%–78% of the total copepod abundance and occur throughout the year. The relative abundance of these dominant copepod species showed no clear seasonal pattern in abundance, suggesting that their populations are relatively stable. Yet, significant differences in the composition and abundance of the remaining non-dominant species resulted in distinctive seasonal communities of copepods being detected. Multivariate multiple regressions revealed that the community structure and species composition fluctuates with monsoonal variables (wind velocity and direction, water temperature) and POC concentration, emphasizing that the differences in water source and food availability are important factors in shaping the distinct structure of the copepod assemblages in tropical coral reef waters of South East Asia.

Spatiotemporal distribution of planktonic copepod communities in Tokyo Bay where Oithona davisae Ferrari and Orsi dominated in mid-1980s

The spatiotemporal distributions of the planktonic copepod communities in Tokyo Bay in 1986–1987, when it was in a more eutrophicated condition than at present, were examined using zooplankton samples collected by vertical hauls of Kitahara’s quantitative net (mesh opening, 0.1 mm) from 19 stations in July, August, October, December 1986 and February 1987. The total abundance of copepods ranged from 3 × 104 to 2750 × 104 ind. m−2 with peaks in July and August and a remarkable decrease in October. Oithona davisae dominated most samples with the subdominant species Acartia omorii in the inner and central areas in December and February, and Paracalanus parvus s.l. in the outer area in October, December and February. The copepod communities in the inner and central areas were classified into 2–4 groups in July, August and October, whereas they mostly comprised a single group in December and February. These differences in distribution pattern might be related to seasonal changes in environmental factors such as river discharge, intrusion of high-salinity outer-bay water, and hypoxic water. In comparison with the community in July 1948, the area of dominance of O. davisae had expanded to the whole bay and A. omorii had decreased in the inner area in July 1986, while other copepods such as P. parvus s.l. and Microsetella norvegica had decreased in the whole bay.

Distribution and community characteristics of planktonic copepods in the northwest coastal waters off Hainan Island

We analyzed the structure, distribution, and seasonal changes of planktonic copepod communities, as well as their relationships with environmental factors using data collected from 21 stations in the northwest coastal waters off Hainan Island between November 2008 and July 2009. A total of 44 species of planktonic copepods was identified, with 25, 23, 22, and 23 species found in autumn (November), winter (January), spring (April) and summer (July), respectively. The dominant species were mainly warm water species, such as Canthocalanus pauper, Subeucalanus subcrassus, Temora turbinate, Acartia spinicauda, Calanopia elliptica and Euchaeta concinna, etc. There were significant changes in copepod abundance among seasons; total copepod abundance was highest in winter with 409 ind./m, followed by autumn with 144 ind./m, spring with 55 ind./m and summer with 17 ind./m, respectively. Distributional data showed that an area of high copepod density appeared in the southern portion of the study area in winter, while there was an area of high copepod density in the center of the survey area in autumn. Copepod abundance was higher in deeper waters, and lower in the coastal areas in spring and summer. Species diversity index was highest in summer and followed by spring, autumn and winter in turn. The evenness index of spring and summer copepod communities was higher than those of autumn and winter. The structure of these planktonic copepod communities reflects tropical and subtropical floristic characteristics. Species composition varied significantly with season, and copepod abundance was noticeably affected by water temperature and diatom cell abundance. We 第 3 期 孙柔鑫等: 海南岛西北沿岸海域浮游桡足类的分布及群落特征 321 detected no obvious correlationship between copepod abundance and salinity.

Invasive copepods in the Lower Columbia River Estuary: Seasonal abundance, co-occurrence and potential competition with native copepods

As part of a multi-year field study to investigate plankton dynamics in the Lower Columbia River Estuary (LCRE), we conducted monthly sampling of the mesozooplankton (> 73 μm) at a station near Astoria, Oregon. The planktonic copepod community was numerically dominated by three non-indigenous species (NIS), Pseudodiaptomus forbesi, Limnoithona tetraspina, and Sinocalanus doerrii, and two native species, Eurytemora affinis and Diacyclops thomasi. However, seasonal co-occurrence of non-indigenous and native copepods was highly variable between species-pairs. The native E. affinis and the non-indigenous S. doerrii showed the greatest temporal overlap (March-October), but other species-pairs also showed periods of considerable overlap during some seasons (e.g., E. affinis and P. forbesi in June-September). Spatial co-occurrence of native and non-indigenous species was also examined in temperature and salinity “space” (rather than geographic space): all six species-pairs (3 non-indigenous species × 2 native species) showed some degree of overlap, with the greatest (proportional) overlap occurring between the native E. affinis and the two nonindigenous species, S. doerrii and P. forbesi. This suggests the potential for competition to occur between native and non-native copepods in the LCRE, although with variation between seasons and species. Future studies are recommended that explicitly test for and distinguish between the relative importance of biological (e.g., competition and predation) and physico-chemical processes (e.g., freshwater runoff, eutrophication) in regulating the population dynamics of native and invasive copepods in the LCRE.

Changes in the planktonic copepod community in a landlocked bay in the subtropical coastal waters of Hong Kong during recovery from eutrophication

Tolo Harbour is a poorly flushed bay in the northeastern corner of Hong Kong. Eutrophication caused by discharge of untreated and secondarily treated sewage into the bay was first detected during the 1970s. Increased nutrient input led to a noticeable increase in algal biomass and algal bloom occurrences. Nutrient reduction measures, including the construction of a pipeline to export all sewage effluents from Tolo Harbour, were introduced during the late 1980s. Decline in nutrient levels and decrease in the number of algal blooms have been recorded since 1998 when all nutrient reduction measures became fully operational. Zooplankton samples collected during 2003–2004 revealed that Tolo Harbour still contained a higher density and lower diversity of planktonic copepods compared to Mirs Bay, a less-polluted sea area outside Tolo Harbour. A comparison between data collected in this study to those collected during 1988–1990, several years before nutrient reduction measures were to be fully implemented, showed a decrease in copepod densities and an increase in copepod diversity. Small copepods, notably species of Paracalanus and Oithona, dominated the copepod communities in both periods, but there was an increase in species evenness during 2003–2004, caused by an increase in the number of dominant species. These observations confirm that eutrophication may lead to increases in copepod densities accompanied by increased dominance of small species.

Summer planktonic copepod communities of Australia's North West Cape (Indian Ocean) during the 1997-99 El Nino/La Nina

The community composition of pelagic copepods near Australia’s North West Cape (21° 49′S, 114° 14′E) was studied during the austral summers of 1997/98 and 1998/99. Most sampling occurred at a shallow (20 m) shelf station and a deeper (90 m) shelf-break station, though on four occasions a set of eight stations were occupied on a 36 km cross-shelf transect. During the El Nino conditions prevalent during the austral summer of 1997/98, episodic upwelling occurred causing intermittent high primary production. During the El Nino conditions of 1997/98, there was a little difference between stations in the spring (October-November), but communities differentiated later in the sampling season (December-February) with a more characteristic inshore community developing at the shelf station. In the La Nina conditions of 1998/99, the community at the shelf break was invariant, but the shelf community was mainly offshore copepods as a result of seasonal downwelling during the spring that was later replaced by an inshore community of more widely distributed species. Over 120 species of copepods were identified, of which the most speciose families were the Corycaeidae (22 spp.), Oncaeidae (>20 spp.), Paracalanidae (15 spp.) and the Oithonidae (11 spp.). Cross-shelf transects confirmed the existence of a distinct inshore community of copepods, dominated by small species of Paracalanidae and Oithonidae, and which was at least twice as abundant as those at the shelf break. In both summers, there was an onshore-offshore gradient in community composition, with the inshore stations characterized by small paracalanid and oithonid species.

Planktonic copepods from temporary marshes in Everglades National Park (Florida, U.S.A.)

During the wet season of 1999–2000, we studied the effects of the hydroperiod and other physical and chemical variables on planktonic copepod communities from six stations in Everglades National Park. Two stations were located in a slough (Taylor Slough 1, Taylor Slough 2) and four stations in the marl prairies of the Rocky Glades (Long Pine Key 7, Long Pine Key 8, Pa-hay-okee, Chekika). During the period of investigation, Taylor Slough sites had the longest hydroperiods, together with Pa-hay-okee, which is located near the eastern edge of Shark River Slough. Long Pine Key 7 and Long Pine Key 8 had the shortest hydroperiods, and Chekika had an intermediate hydroperiod. The pineland edge sites in the southern Rocky Glades (Long Pine Key) had higher numbers of individuals, and high percentages of larval stages, especially at the end of the wet season. The pineland ecotone is morphologically very heterogeneous, with solution holes in the limestone bedrock that provide below-ground refugia when there is no water on the marsh surface. The slough stations had the lowest numbers of individuals, as well as Chekika in the Rocky Glades, probably as a consequence of the altered water quality and hydropatterns caused by water management structures and operations We collected two species of calanoids, 18 cyclopoids, and three harpacticoids. The most abundant species were Acanthocyclops robustus, Tropocyclops prasinus mexicanus, Arctodiaptomus floridanus, Mesocyclops americanus, Macrocyclops albidus, Osphranticum labronectum, Microcyclops varicans, Microcyclops rubellus, Eucyclops conrowae, and Mesocyclops edax. Of these species, T. prasinus mexicanus and A. floridanus seemed to be adapted to short-hydroperiod habitats, M. rubellus and M. varicans to longer hydroperiod habitats, and E. conrowae to high conductivity habitats. Acanthocyclops robustus, M. albidus, and O. labronectum were dominant regardless of hydroperiod. As regards the temporal distribution, A. robustus was abundant throughout the entire wet season, M. edax, M. rubellus, M. americanus and M. varicans were most abundant in mid-wet season, in September–October, and T. prasinus mexicanus, M. albidus, and E. conrowae were abundant late in the wet season, in winter. The two calanoids only slightly overlapped in time: A. floridanus was abundant at the beginning of the wet season, in July–August, and O. labronectum was abundant at the end of the wet season, in December.

Predator‐Prey Relationships in an Estuarine Littoral Copepod Community

Seasonal divergences of planktonic copepod communities in a marine eelgrass bed and adjacent unvegetated channel habitats were associated with increases in predator abundance in the littoral habitat. During midsummer, when planktivorous silversides, Menidia menidia, were abundant in the eelgrass bed, pelagic copepod densities were significantly reduced in the eelgrass bed, relative to channel abundances. Differences declined overnight, when fish were not feeding, and were reestablished after dawn. In late winter, coincident with the arrival of large numbers of postlarval fish in the eelgrass bed, there was selective reduction of juvenile Centropages spp. in the eelgrass bed, relative to channel abundances. Field and laboratory experiments indicate that these differences were due to intense predation by planktivorous fish. However, the littoral copepod Pseudodiaptomus coronatus appeared unaffected by the intense predation in the eelgrass bed. Laboratory experiments demonstrated that its epibenthic habit and cryptic coloration allow P. coronatus to utilize refuges in the littoral habitat, and that prey selection by two fish species differed due to differences in foraging behavior.

Distribution and Community Structure of Estuarine Copepods

Distribution, abundance, and community structure were studied over a 30 month period in the planktonic copepod community of the estuaries near Beaufort, North Carolina. Many of the copepod species showed a demersal distribution during the day and entered the surface waters at night. Several species were largely confined to vegetated littoral areas during the day. The copepod community showed consistent trends of seasonal abundance and succession of dominant species which differed greatly from those found by previous workers, whose methods were inadequate to sample quantitatively the small, demersal copepods which dominated the community. Copepod abundances were higher than found in previous studies and were correlated with water temperature. Species composition changed from a winter community dominated byCentropages spp., to a spring community dominated byAcartia tonsa, to a summer community jointly dominated byParacalanus crassirostris andOithona spp. Copepods were much more important grazers in these estuaries than previous studies had concluded.

Interactive effects of temperature and predation on an estuarine zooplankton community

The winter planktonic copepod community of the estuaries near Beaufort N.C. underwent a consistent transition from dominance by Acartia tonsa Dana to dominance by Centropages spp., which was associated with unpredictable decreases in water temperature and increases in abundance of predatory mysids. Centropages subsequently remained dominant until spring. Experimental manipulations of water temperature and mysid abundance in enclosures showed that copepod species composition was determined by an interaction of direct temperature effects with predatory interactions among copepods and mysids. Low temperatures stimulated recruitment of Centropages spp. and inhibited recruitment of Acartia tonsa. Temperature decreases also apparently stimulated migration of mysids into the study area. While A. tonsa was dominant, selective predation by mysids reduced the relative abundance of A. tonsa, but after Centropages became dominant mysid predation had no effect on copepod species composition. Predation by Centropages on the nauplii of other species probably contributed to its persistent dominance in the estuary. Rising temperatures in the spring favored recruitment of Acartia tonsa and inhibited Centropages recruitment. Selective predation by fish entering the estuary in spring may have contributed to the decline in abundance of Centropages spp. and mysids.