斑马鱼脑细胞凋亡基因对束丝藻毒素致毒的响应

水华束丝藻是淡水湖泊中常见的水华蓝藻,是我国滇池冬春季节常见的优势种群,因其产生麻痹性贝类毒素,损伤人和动物的神经系统而倍受关注。但有关该毒素对动物神经系统损伤的研究较少,特别是对水生脊椎动物中枢神经系统损伤的研究尚无报道,为此本研究通过腹腔注射5.3μg STXeq/kg bw束丝藻毒素,研究了24h内该藻毒素对斑马鱼脑组织超微结构损伤及脑细胞凋亡基因表达的影响,以揭示该毒素对脑组织的损伤及其脑细胞在基因水平对该毒素的响应机理。研究表明,束丝藻毒素引起斑马鱼脑组织超微结构损伤,出现细胞膜发泡和形成凋亡小体等典型的细胞凋亡结构;从分子水平进一步分析显示,该毒素引起脑细胞p53、bax、caspase-3和c-jun等凋亡相关基因的表达上调,其上调量分别是对照组表达上调量的1.92、1.55、1.63和1.55倍,且具有时间-效应关系。这说明该毒素能通过引起脑细胞凋亡基因的表达异常,使脑细胞出现凋亡性形态损伤而导致脑细胞死亡;斑马鱼脑细胞可通过启动p53→bax→caspase-3线粒体径路实现其对该毒素的响应机制;束丝藻毒素具有损伤鱼类脑的神经毒性;这是束丝藻毒素引起脑细胞凋亡基因表达异常及超微结构损伤的直接证据,也是脑细胞在基因水平对束丝藻毒素积极响应分子机理的首次报道。     

POPULATION GENETICS OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE) IN NARRAGANSETT BAY1

During a two year period 457 clones of the diatom Skeletonema costatum were isolated prior to and during the summer-fall and winter-spring blooms of this species in Narragansett Bay, R.I. Their allozyme banding patterns were examined for 5 enzyme loci. Genotypic frequencies indicated that the winter bloom populations were genetically different from the prevalent summer bloom populations of the same species. Genetic differences between seasonal blooms are as great as those found between species of terrestrial organisms, but are not accompanied by morphological variation. Although blooms have distinct prevalent forms, they are not genetically homogeneous. No single clone is ever representative of all populations of S. costatum. The dynamics of these allochronic populations appear to be governed by a form of cyclic natural selection, and are probably a regular feature of the cycles of abundance of this species in this area. These results cast doubt on some of the assumptions often made in the “autecological approach” to phytoplankton ecology. This study comprises the first quantitative examination of the population genetics of a microalga.     

“Windows of opportunity” for dinoflagellate blooms: Reduced microzooplankton net growth coupled to eutrophication

Links between eutrophication, plankton community structure, microzooplankton grazing and dinoflagellate abundance were investigated in two tributaries of the Chesapeake Bay, the Choptank and Patuxent Rivers (MD, USA). Sampling and experiments were conducted during the spring of consecutive dry (below average freshwater flow) and wet (above average freshwater flow) years. During the wet year (2003), dissolved inorganic nitrogen, phytoplankton, and copepod biomass, but not microzooplankton abundance, were greater than in the dry year. In 2003, but not 2002, small cell size photosynthetic dinoflagellates were abundant and blooms occurred in both rivers. Average potential microzooplankton grazing pressure on small dinoflagellates was spatially and temporally variable, but was not significantly different between years. Our data suggest that the variability in microzooplankton grazing pressure provided “windows of opportunity” for net growth of dinoflagellates in response to nutrient loading. The lack of net population growth of micrograzers in response to increases in dinoflagellate prey allowed dinoflagellate blooms to reach relatively high densities, however grazing also appeared to be important in limitation or demise of some blooms. We hypothesize that uncoupling of micrograzer–prey dynamics was partly due to strong top-down control by copepods of microzooplankton in the proportionately more eutrophic year, and perhaps also due to inhibition of microzooplankton grazing/growth once dinoflagellate densities are high.     

Long-term changes in Noctiluca scintillans blooms along the Chinese coast from 1933 to 2020

Noctiluca scintillans is one of the most common harmful algal species and widely known due to its bioluminescence. In this study, the spatial distribution, seasonal variations, and long-term trends of N. scintillans blooms in China and the related drivers were analyzed and discussed. From 1933 to 2020, a total of 265 events of N. scintillans blooms were recorded in Chinese coastal waters, with a total duration of 1052 days. The first N. scintillans bloom occurred in Zhejiang in 1933, and only three events were recorded before 1980. From 1981 to 2020, N. scintillans caused harmful algal blooms (HABs) almost every year, both the average duration and the proportion of multiphase HABs showed an increasing trend. 1986–1992, 2002–2004, and 2009–2016 were the three peak periods with a frequency of no less than five events of N. scintillans blooms per year. In terms of spatial distribution, N. scintillans blooms spread from the Southeast China Sea to the Bohai Sea after 2000, Guangdong, Fujian, and Hebei were the three provinces with the highest numbers of recorded events of N. scintillans blooms. Moreover, 86.8% of the events of N. scintillans blooms occurred in spring (March, April, and May) and summer (June, July, and August). Among environmental factors, the dissolved inorganic phosphate, dissolved silicate and chemical oxygen demand were significantly correlated with the cell density of N. scintillans during N. scintillans blooms, and most of N. scintillans blooms were recorded in the temperature range of 18.0–25.0°C. Precipitation, hydrodynamics, water temperature, and food availability might be the main factors affecting the spatial–temporal distribution of N. scintillans blooms along the Chinese coast.     

Monitoring of the toxic dinoflagellate Alexandrium catenella in Osaka Bay,Japan using a massively parallel sequencing (MPS)-based technique

Since 2002, blooms of Alexandrium catenella sensu Fraga et al. (2015) and paralytic shellfish toxicity events have occurred almost yearly in Osaka Bay, Japan. To better understand the triggers for reoccurring A. catenella blooms in Osaka Bay, phytoplankton community was monitored during the spring seasons of 2012–2015. Monitoring was performed using massively parallel sequencing (MPS)-based technique on amplicon sequences of the 18S rRNA gene. Dense blooms of A. catenella occurred every year except in 2012, however, there was no significant correlation with the environmental parameters investigated. Plankton community diversity decreased before and middle of the A. catenella blooms, suggesting that the decline in diversity could be an indicator for the bloom occurrence. The yearly abundance pattern of A. catenella cells obtained by morphology-based counting coincided with the relative sequence abundances, which supports the effectiveness of MPS-based phytoplankton monitoring.     

Strong effects of amoebae grazing on the biomass and genetic structure of a Microcystis bloom (Cyanobacteria)

Despite its importance for bloom toxicity, the factors determining the population structure of cyanobacterial blooms are poorly understood. Here, we report the results of a two‐year field survey of the population dynamics of Microcystis blooms in a small hypertrophic urban pond. Microscopic enumeration of Microcystis and its predators and parasites was combined with pigment and microcystin analysis and denaturing gradient gel electrophoresis of the ITS rDNA region to assess population dynamics and structure. Two main Microcystis morpho‐ and ITS types were revealed, corresponding to M. aeruginosa and M. viridis. In both years, high population densities of naked amoebae grazing on Microcystis coincided with rapid decreases in Microcystis biomass. In one year, there was a shift from heavily infested M. aeruginosa to the less‐infested M. viridis, allowing the bloom to rapidly recover. The preference of amoebae for M. aeruginosa was confirmed by grazing experiments, in which several amoeba strains were capable of grazing down a strain of M. aeruginosa, but not of M. viridis. Zooplankton and chytrid parasites appeared to be of minor importance for these strong and fast reductions in Microcystis biomass. These findings demonstrate a strong impact of small protozoan grazers on the biomass and genetic structure of Microcystis blooms.     

A model for seasonal phytoplankton blooms

We analyse a generic bottom-up nutrient phytoplankton model to help understand the dynamics of seasonally recurring algae blooms. The deterministic model displays a wide spectrum of dynamical behaviours, from simple cyclical blooms which trigger annually, to irregular chaotic blooms in which both the time between outbreaks and their magnitudes are erratic. Unusually, despite the persistent seasonal forcing, it is extremely difficult to generate blooms that are both annually recurring and also chaotic or irregular (i.e. in amplitude) even though this characterizes many real time-series. Instead the model has a tendency to 'skip' with outbreaks often being suppressed from 1 year to the next. This behaviour is studied in detail and we develop analytical expressions to describe the model's flow in phase space, yielding insights into the mechanism of the bloom recurrence. We also discuss how modifications to the equations through the inclusion of appropriate functional forms can generate more realistic dynamics.     

Molecular approaches to diagnosing nutritional physiology in harmful algae: Implications for studying the effects of eutrophication

Every year harmful algal blooms (HABs) cause serious impacts to local economies, coastal ecosystems, and human health on a global scale. It is well known that nutrient availability can influence important aspects of harmful algae biology and ecology, such as growth, toxin production, and life cycle stage, as well as bloom initiation, persistence and decline. Increases in the rate of supply of organic matter to ecosystems (eutrophication) carries many possible ramifications to coastal systems, including the potential for nutrient enrichment and the potential for stimulation of harmful algal blooms. Traditional studies on algal nutrition typically use either cultured isolates or community level assays, to examine nutrient uptake, nutrient preference, elemental composition, and other metrics of a species’ response to nutrients. In the last decade, technological advances have led to a great increase in the number of sequences available for critical harmful species. This, in turn, has led to new insights with regards to algal nutrition, and these advances highlight the promise of molecular technologies, and genomic approaches, to improving our understanding of algal nutrient acquisition and nutritional physiological ecology, in both cultures and field populations. With these developments increased monitoring of nutritional physiology in field populations of harmful algae will allow us to better discriminate how eutrophication impacts these groups.     

The effects of sea urchin grazing and drift algal blooms on a subtropical seagrass bed community

Subtropical seagrass beds can be subject to relatively high levels of direct herbivory and large blooms of drift algae, both of which can have important effects on the floral and faunal components of the community. Caging experiments were used to investigate these factors in a Thalassia testudinum bed in Biscayne Bay, Florida. Abundance of sea urchins, Lytechinus variegatus, and drift algae was manipulated within the cages. Naturally occurring levels of urchin grazing do not appear to affect the T. testudinum population. With experimentally increased urchin densities in the winter, seagrass shoot density and aboveground biomass decreased significantly. Similar effects were not detected in the summer, indicating that the impact of grazing on T. testudinum is lessened during this time of year. Shoot density was more vulnerable to grazing than aboveground biomass. This may be a result of grazing-induced increases in seagrass productivity, in which the remaining shoots produce more or longer leaves. In the winter, drift algal blooms form large mats that cover the seagrass canopy. Under the normal grazing regime these algal blooms do not have significant negative effects on the seagrass. With increased grazing pressure, however, there is a synergistic effect of grazing and drift algae on seagrass shoot density. At intermediate urchin density (10 per m(-2)), cages without algae did not undergo significant decreases in shoot density, while those with algae did. At the high density of urchins, the number of seagrass shoots in cages both with and without algae decreased, but the effect was more pronounced for cages with algae. Invertebrate abundance at the field site was low relative to other seagrass beds. There were no discernible effects, either positive or negative, of urchin and algae manipulations on the sampled invertebrate community.     

Local effects of wind speed and direction on the phytoplankton of the Southern Bight

The causes of the exceptionally early blooms of Ceratium spp.in the Southern Bight of the North Sea during the early 1970sare re-assessed. This localised event is found to coincide witha change in the meridional circulation over the North Sea inthe late winter and early spring, with abnormally strong northerliesduring the 1960s giving way to strengthened southerlies duringthe early 1970s. Such a change in wind direction can be expected(both from observation and simulation) to bring about a lesswidespread distribution of turbid coastal water in the SouthernBight and the marked reduction in windfetch may also have servedto decrease watercolumn turbidity through its effect on theincidence of long-period swell. These processes may be reinforcedby associated changes in the quantity of turbid runoff dischargedby the Rhine. The advanced blooms of Ceratium spp. in the early1970s are attributed both to these effects and to an increasedfrequency of light winds (decreased wind mixing) in the earlymonths of the year.     

Interannual variability of cyanobacterial blooms in lake erie

After a 20-year absence, severe cyanobacterial blooms have returned to Lake Erie in the last decade, in spite of negligible change in the annual load of total phosphorus (TP). Medium-spectral Resolution Imaging Spectrometer (MERIS) imagery was used to quantify intensity of the cyanobacterial bloom for each year from 2002 to 2011. The blooms peaked in August or later, yet correlate to discharge (Q) and TP loads only for March through June. The influence of the spring TP load appears to have started in the late 1990 s, after Dreissenid mussels colonized the lake, as hindcasts prior to 1998 are inconsistent with the observed blooms. The total spring Q or TP load appears sufficient to predict bloom magnitude, permitting a seasonal forecast prior to the start of the bloom.     

A MOLECULAR AND PHENOTYPIC ANALYSIS OF NODULARIA (CYANOBACTERIA) FROM THE BALTIC SEA

The filamentous diazotrophic cyanobacterium Nodularia forms water blooms each year in the Baltic Sea. Filaments isolated from such water blooms vary in their trichome width, degree of coiling, and properties of their gas vesicles; previously, these characters have been used to classify individuals to species level. To test the validity of such a phenotypic classification, we determined the nucleotide sequences for a region of the phycocyanin locus that includes a noncoding intergenic spacer (PC-IGS), the IGS between two adjacent copies of the gvpA gene (which encodes the main structural gas vesicle protein) and the rDNA internal transcribed spacer (rDNA-ITS), for 13 clonal Nodularia isolates from the Baltic Sea during August 1994. The complete 16S-rDNA sequence was determined for three isolates and was found to be identical in each of them. Molecular sequences for noncoding regions of the genome were used to assign isolates to three groups on the basis of PC-IGS, two groups on the basis of gvpA -IGS, and three groups on the basis of rDNA-ITS. No consistent correlation was found between genotype and any of the phenotypic features examined, and no link was found between any of these features themselves, indicating that these characters are not useful for placing Nodularia isolates into meaningful taxonomic groups. The PC-IGS, gvpA -IGS, and rDNA-ITS genotypic groupings were not congruent. This might indicate that gene flow occurs between individuals in Nodularia populations.     

Assessment of brown tide blooms, caused by Aureococcus anophagefferens, and contributing factors in New Jersey coastal bays: 2000–2002

A 3 year study (2000–2002) in Barnegat Bay-Little Egg Harbor (BB/LEH), New Jersey (USA), was conducted by the New Jersey Department of Environmental Protection, Division of Science Research and Technology (DSRT) in cooperation with several partners to assess brown tide blooms in coastal waters in NJ. Water samples were collected by boat and helicopter at coastal stations from 2000 to 2002 along with field measurements. Aureococcus anophagefferens were enumerated and associated environmental factors were analyzed. A. anophagefferens abundances were classified using the Brown Tide Bloom Index and mapped, along with salinity and temperature parameters, to their geo-referenced location using the ArcView GIS. The highest A. anophagefferens abundances (>10⁶ cells ml⁻¹), including category 3 blooms (≥200,000 cells ml⁻¹) and category 2 blooms (≥35,000 to ≤200,000 cells ml⁻¹), recurred during each of the 3 years of sampling and covered significant geographic areas of the estuary, especially in Little Egg Harbor. While category 3 blooms were generally associated with warmer water temperatures (>16 °C) and higher salinity (>25–26 ppt), these factors were not sufficient alone to explain the timing or distribution of A. anophagefferens blooms. There was no significant relationship between brown tide abundances and dissolved organic nitrogen measured in 2002 but this was consistent with other studies. Extended drought conditions, with corresponding low freshwater inputs and elevated bay water salinities, occurring during this time were conducive to blooms. A. anophagefferens abundances were well above the reported levels that have been reported to cause negative impacts on shellfish. It was shown that over 50% of the submerged aquatic vegetation (SAV) habitat located in Barnegat Bay/Little Egg Harbor was categorized as having a high frequency of category 2 or 3 blooms for all 3 years.     

Large-scale patterns of Nodularia spumigena blooms in Pyramid Lake,Nevada, determined from Landsat imagery: 1972–1986

Magnitude and long-term periodicity of summer-autumn blooms of the nitrogen-fixing cyanobacterium, Nodularia spumigena, were characterized for hyposaline Pyramid Lake, Nevada, from Landsat MSS band 3 film negatives. Predicted lakewide mean chlorophyll a concentrations for Landsat overpasses during the July–October Nodularia bloom season ranged from 27 to 72 mg m^–3 with an overall average concentration of 32 ± 7 mg m^–3 between 1972 and 1986. Nodularia blooms were usually annual events. Blooms were not observed on Landsat images in only three of 15 years (1973, 1980, 1982) and midsummer calcium carbonate whitings occurred in two of these years (1973, 1980). Magnitude of Nodularia blooms was highly variable among years and very large blooms, where maximum mean chlorophyll a concentration exceeded one standard deviation of the 15 year overall mean (> 39 mg m^–3) appeared in 1974, 1975, 1977, 1979, 1984, 1985 and 1986. Very large early-July blooms always occurred during or following years of above average fluvial discharge to Pyramid Lake (1984–1986) and were associated with meromixis produced by the large influx of freshwater.Several problems arise using Landsat remote sensing to estimate magnitude and periodicity of scum-forming blue-green algal blooms. These complications may reduce accuracy and precision of phytoplankton biomass estimates made from Landsat images. Nevertheless, Landsat remote sensing enabled us to quantify relative bloom magnitude with limited collection of ground-based data and at a large-scale temporal and spatial resolution not possible using alternative methodologies.     

Cooccurrence of elevated urea levels and dinoflagellate blooms in temperate estuarine aquaculture ponds

In hybrid striped bass aquaculture ponds, dinoflagellate blooms were found on 10 of 14 occasions to co-occur with concentrations of urea in excess of 1.5 microM nitrogen. When urea levels were <1.5 microM nitrogen, on seven occasions, no evidence of dinoflagellate blooms was observed in these ponds.     

High Resolution Spatio-temporal Detection of Potentially Harmful Dinoflagellates in Confined Waters of the NW Mediterranean

A systematic sampling programme was carried out in a large numberof confined waters (principally harbours) along the Catalancoast (NW Mediterranean) in the context of a new MonitoringProgramme. This Monitoring Programme was associated not onlywith areas subject to aquaculture activities, and thereforeunder legislation, but also with confined areas with a highrisk of harmful algal blooms (HABs) occurrence, in order toprovide an early warning of potentially widespread HABs. Thesystematic programme was performed weekly in summer and bi-monthlyin winter for five years. The main results were: (i) the detectionof many harmful species and the presence of high numbers ofharmful dinoflagellates, mainly of the genera Alexandrium andDinophysis; (ii) the detection of Alexandrium catenella, newin the study area, which had hardly ever been detected in theMediterranean Sea; (iii) the presence of some potentially harmfulspecies, including Dinophysis sacculus, present at all periodsof the year; (iv) bloom recurrence in several stations; (v)occasional coincidence of small-scale blooms, such as thoseconfined inside the harbours, with widespread blooms (mesoscaleblooms) of the same organism. The implications of this highfrequency of HAB detection is discussed in relation to the suitabilityof this sampling programme (focused on confined waters) forthe early detection of algal blooms.     

Cochlodinium polykrikoides blooms and eco-physical conditions in the South Sea of Korea

Eco-physical conditions for the initiation and termination of Cochlodinium polykrikoides blooms in the South Sea of Korea are examined in this paper. The C. polykrikoides blooms generally occur in the sea near Naro-Do in late August every year. The submarine canyon near Naro-Do plays an important role in surface water intrusion from the open ocean driven by northeasterly winds. In late August, the monsoonal wind system in Korea changes from southwesterly to northeasterly winds, causing Ekman transport of warm, fresh Changjiang Diluted Water (CDW) into the sea near Naro-Do and creating a front between inland sea water and CDW. Along the front, aggregation of single C. polykrikoides cells in the CDW and downwelling yield favorable eco-physical conditions for development of C. polykrikoides blooms. When typhoons and strong northeasterly winds bring vertically well-mixed East China Sea water into the sea near Naro-Do again in September, the eco-physical conditions favor diatom growth and lead to the termination of C. polykrikoides blooms.     

三峡水库支流拟多甲藻水华的形成机制

三峡水库支流的拟多甲藻水华发生已成为近年的常态,但是其发生机制依然不清楚。2009年到2011年期间,对拟多甲藻水华频发的童庄河回水区进行重点监测,并扩展到三峡水库长江干流及26条支流未淹没区和回水区浮游植物的四季调查。结果表明,四季调查中,拟多甲藻出现率、平均密度、最大密度和最大优势度,4月最高,相同季节,回水区最高。2—4月,童庄河回水区各点拟多甲藻密度均为升高到下降变化,最高密度自上游至下游大幅下降。2010年,拟多甲藻水华于2月最先在童庄河回水区上游出现,逐步向中下游发展,维持一定规模和时间后消退。与此同时,长江干流拟多甲藻出现率、密度和最大优势度大幅低于童庄河回水区。童庄河回水区发生(2005年、2007年和2010年)比不发生(2009年)拟多甲藻水华年份,三峡水库1—3月日出库流量(平均值4489.9—5623.3 m3/s)较小、1—2月水位日变幅(平均值0.148 m、0.246 m)和2月水位日升降(平均值-0.223 m)较大。研究认为,藻类在适宜水温时形成水华,2—4月支流回水区水温适宜、氮磷含量满足甲藻营养能力和生活习性需要。拟多甲藻能否形成水华,首先取决于回水区上游是否存在满足要求的水动力条件。其次,三峡水库出库流量、水位波动等水文条件,通过改变回水区上游水动力条件和回水区流速,影响水华能否形成及形成时间、程度、范围和维持时间。由于尺度效应不同,三峡水库相同水文条件对不同位置支流拟多甲藻水华形成的影响不一样。     

Ecology of phytoplankton communities dominated by Aureococcus anophagefferens: the role of viruses, nutrients, and microzooplankton grazing

We investigated the impact of viruses, nutrient loading, and microzooplankon grazing on phytoplankton communities in two New York estuaries that hosted blooms of the brown tide alga Aureococcus anophagefferens during 2000 and 2002. The absence of a bloom at one location during 2002 allowed for the fortuitous comparison of a bloom and non-bloom year at the same location as well as a comparison of two sites experiencing bloom and non-bloom conditions during the same year. During the study, blooms were found at locations with high levels of dissolved organic nitrogen and lower nitrate concentrations compared to a non-bloom location. Experimental additions of inorganic nitrogen and phosphorus yielded growth rates within the total phytoplankton community which significantly exceeded control treatments in 83% of experiments, while A. anophagefferens experienced significantly increased growth during only 20% of experimental inorganic nutrient additions. Consistent with prior research, these results suggest brown tides are not caused by eutrophication, but instead are more likely to occur when sources of labile DOM are readily available. Microzooplankton grazing rates on the total phytoplankton community during a bloom were lower than grazing rates at a non-bloom site, and grazing rates on A. anophagefferens were lower than grazing rates on the total community on some dates, suggesting that reduced grazing mortality may also promote brown tides. Mean densities of viruses during blooms (3 × 10⁸ ml⁻¹) were elevated compared to most estuarine environments and were twice the levels found at a non-bloom site. Experimental enrichment of the natural viral densities yielded a significant increase in A. anophagefferens growth rates relative to control treatments when background levels of viruses were low (<1.7 × 10⁸ ml⁻¹), suggesting that viruses may promote bloom occurrence by regenerating DOM or altering the composition of microbial communities.     

Comparative life histories in the genera Calanus and Neocalanus in high latitudes of the northern hemisphere

At least nine species of Calanidae occupy the area of interest, four in the Atlantic and five in the Pacific. All store wax esters and probably can undergo diapause. Latitudinally overlapping or onshore — offshore associations of two or more species occur in both oceans. Interzonals, with reduced mouth parts in the adult female, are endemic to the Pacific subarctic gyre where their life cycles are completed in one year. Presumably its nearly closed circulation and environmental stability have favored the evolution of endemic species well adapted to those conditions. Lack of ice- and/or salinity-induced stability also limits blooms there. The sub-arctic Atlantic contains several smaller oceanographic features, open to both arctic and Atlantic influences and populated by species of different origins, arctic species can behave as interzonals but may also require two or more years to complete their life cycles. Females may need to feed one year to reproduce the next and therefore they retain functional mouthparts. In some places in the North Atlantic, blooms may start in the sub-ice zone and seed the remaining euphotic zone. There the earliest stages of some the Calanus species can develop close to the ice, using primarily ice algae as food, while the remaining stages are adapted to utilize brief periods of intense primary production in the water column. Salinity-induced stability and shallow water favor blooms in the boundary waters of both oceans, which may be of greater importance in the Atlantic because of the proportionally greater area of continental shelf there. In both oceans the smaller species of Calanidae can produce up to three generations per year.