Non-predatory mortality assessment of zooplankton in Magdalena Bay, Mexico, during El Niño 2015.

doi:10.21203/rs.3.rs-3443988/v1

During 2015, monthly zooplankton sampling and measurements of surface temperature (SST), salinity, dissolved oxygen and chlorophyll a were conducted. Collections were made during neap tides at four locations between the inner and near the mouth of Magdalena Bay, Mexico. Thirty-three taxonomic groups were identified, and the most abundant taxa were copepods, diplostracans, decapods, ichthyoplankton (fish eggs) and chaetognaths. Zooplankton abundance did not vary significantly over time, but did vary between sampling stations. SST and salinity were significantly correlated with the spatial distribution of organisms. Differences were found between the mortality percentages for the sampling stations and also for the taxonomic groups analyzed (Copepods 18%; Decapods 32%; Chaetognaths 33%), which implies the importance of carrying out mortality determination analyses in ecological studies of zooplankton.

live/dead ratio

copepods

decapods

chaetognaths

zooplankton abundance

Marine zooplankton is the energy transfer pathway to higher trophic levels, produced by phytoplankton, as well as playing a vital role in biogeochemical cycles in the marine ecosystem (Gocke and Lenz 2004).

To address structural changes in the zooplankton community, functional diversity in the pelagic ecosystem is used (Lavaniegos et al. 2015), as taxonomic groups are relatively easy to identify and can be counted from a fraction of the sample (Ohman and Lavaniegos 2002). In addition, changes in zooplanktonic structure are evident at the taxonomic group level, such as the decline in abundance and biomass of salps during the 1977–1998 warm regime off southern California (Lavaniegos and Ohman 2007).

In Magdalena Bay (MB), an ecosystem of high variability and biological complexity (Funes-Rodríguez et al. 2007, 2022), knowledge of zooplankton community structure is fragmented and how environmental variability influences community attributes has not been elucidated, despite the ecological role zooplankton play in the food web.

In 2015 the El Niño event in the Eastern Tropical Pacific was recorded from the second half of that year (Bond et al. 2015; Robinson 2016; Durazo et al. 2017) and had a notable influence on the hydrological characteristics in Magdalena Bay; positive temperature anomalies were recorded throughout most of the year, particularly at oceanographic stations near the mouth (June to December), due to the inflow of warm ocean water into the bay (Jiménez-Quiroz et al. 2019). However, it is known that SST increase in the North Pacific Ocean was recorded from 2013 to 2015 (Leising et al. 2015; Jacox et al. 2016; Zaba and Rudnick 2016) due to the succession and superposition of The Blop (TB) and a warm temperature anomaly that extended over the Mexican Pacific during 2014 (Jiménez-Quiroz et al. 2019). TB was a large warm water mass in the Pacific Ocean off the coast of North America that modified atmospheric and marine temperature, wind patterns, upwelling strength, and productivity from Alaska to Baja California (Leising et al. 2015; McClatchie et al. 2016; Robinson 2016; Zaba and Rudnick 2016). These events altered the atmospheric and oceanic circulation, leading to weakening of the California Current and limitation of nutrient advection from the North Pacific to Baja California (Mcclatchie et al. 2016; Gómez-Ocampo 2017; Alemany-Rodriguez et al. (in press).

In this context, the objective of this paper was to analyze the zooplankton community structure linked to environmental variability during El Niño in 2015, as well as the ratio of dead/live zooplankton in Magdalena Bay. Based on previous knowledge it is expected that the community is dominated mainly by copepods and that the proportion of dead organisms will be higher with increasing surface temperature in Magdalena Bay.

Monthly zooplankton and water samples at four oceanographic stations were collected along the coast of Magdalena Bay during 2015 on neap tides (Fig. 1). Zooplankton tows were shallow for 5 min (1.5 m s^− 1 velocity) with a standard cone net (1.5 m long, 0.60 m mouth diameter, 505 µm mesh) equipped with a digital flowmeter (General Oceanics, Miami, FL, USA) and a soft filtering cod end. Sea surface temperature (SST) and salinity were recorded with a CTD (Sea-Bird Scientific, Bellevue, WA, USA). Surface water samples for measuring dissolved oxygen (DO) and chlorophyll a (Chla) concentrations were obtained with a 5 L Niskin bottle. DO was measured according to the Winkler procedure (Strickland and Parsons 1972), and chlorophyll a was measured according to Jeffrey and Humphrey (1975), using a PerkinElmer Lambda 2 spectrophotometer (Shelton, CT, USA). Prior to each tow to minimize accidental inclusion of dead organisms from previous stations, the net was thoroughly rinsed. Once the sample was obtained, a neutral red solution was added to each sample (1.5 ml per liter, final concentration 1.5:100,000). For exceptionally abundant samples with high concentrations of phytoplankton or debris, up to an additional 3.0 ml of neutral red was added. After addition of the vital dye, samples were incubated for 15 min at ambient temperature. Subsequently, the samples were sieved, rinsed and fixed with formaldehyde (4%) and 12.5 ml aliquots were extracted from each sample using a Stempel pipette. Zooplankton were identified and counted to the level of taxonomic groups using the criteria and keys of Tregouboff and Rose (1957), Smith and Johnson (1977), Boltovskoy (1981), Todd and Laverack (1991) and Gasca and Suárez-Morales (1996); while the number of stained and unstained organisms was recorded for copepods, decapods and chaetognaths. Abundance data were standardized to 100 m³ of water (Smith and Richardson 1977).

Statistical analyses to identify significant differences in the monthly and spatial variability of environmental variables and zooplankton groups were performed using the Kruskal-Wallis (KW) test.

To examine the spatio-temporal hydrological and biological variability a Canonical Correspondence Analysis (CCA) was performed (Ter Braak 1988), to establish the level, significance and intensity of the probable influence of environmental variables on biological ones (PcOrd V6). For this, taxonomic groups representing less than 0.1% of the total abundance recorded were not considered.

The analysis of the live/dead ratio by sampling station and by month was carried out on copepods, decapods and chaetognaths as they were the dominant taxonomic groups.

Environmental conditions.

Sea surface temperature (SST) showed significant variability (p < 0.05) during the study period. The average temperature was comparatively lower in the first half of the year, with values fluctuating between 19.0-22.6°C, with the lowest values in April and May (19.2 and 19.5, respectively). Temperature increased and reached its maximum values between July and September (27.0–29.0°C), decreasing again during the last quarter of the year (Fig. 2 A). Salinity did not present significant differences (p ≥ 0.05) during 2015. However, it was observed that during the first half of the year there was a greater dispersion of data related to salinity differences between interior and near-mouth stations; during the second half of the year, data dispersion was lower. It is worth mentioning that even without significant temporal differences, the lowest average salinity values were observed in November and December (34.4) and the highest in August (35.1) (Fig. 2 B).

Dissolved oxygen concentration showed significant changes throughout the year (p < 0.05) (Fig. 2 C). The increase was observed from late winter (March) until reaching a maximum in July (7 ml L^− 1), beginning to decrease during the second half of the year, with minimum values observed in November and December (4.9 and 4.7 ml L^− 1, respectively).

Chlorophyll a (Chla) concentration did not show significant differences during the study period (p ≥ 0.05) (Fig. 2 D). However, comparatively higher concentrations were observed during the first half of the year (except April) in the range of 1–2.5 mg m^− 3, with a maximum value recorded during May. In contrast, during the second half of the year average values remained low (< 1 mg m^− 3), except October (1.5 mg m^− 3). The highest values were found at the inner bay stations (Punta Gato and Palmita) and the lowest at the stations near the mouth (Baja Seas and Punta Entrada).

Zooplankton Community Structure

A community of 33 zooplankton groups was identified, in which copepods, diplostracans, decapods, chaetognaths and fish eggs outstand for their high frequency of occurrence and relative abundance (80% approx.) (Table 1). Copepods were the most abundant taxonomic group throughout the year and in all sampling seasons.

Zooplankton abundance (Fig. 3 A) did not show a defined monthly variability, as it averaged less than 50,000 organisms/100m³, with no significant differences observed (p ≥ 0.05). The maximum values (80,000 organisms/100m³) were recorded during the month of August. At the sampling stations (Fig. 3 B), significant differences in zooplankton abundance were observed between the Punta Gato station and the other stations (p < 0.05). Punta Gato had a markedly higher average abundance (80,000 organisms/100m³), and the Palmita, Baja Seas and Boca stations had similar average abundances (less than 30,000 organisms/100m³).

Relationship between taxonomic groups and environmental variables

Statistical analysis showed a high correlation between environmental variables with sampling sites and months, as well as with taxonomic groups (R = 0.82; R = 0.71; Fig. 4 A and B; Table 2). Components 1 and 2 explained 21.3% (P < 0.001) of the variance in zooplankton abundance. On axis 1, zooplankton was correlated with SST (R = 0.84). Salinity showed an inverse correlation on axis 2 (R = -0.62), while Chla and OD showed no correlation on any axis (Fig. 4; Table 2). The arrangement of the taxonomic groups (Fig. 4 A) was relatively homogeneous with the environmental variables. The association of Chla was most evident for diplostracans and appendicularians, while SST was most evident for mainly salps and jellyfish. OD and salinity were associated mainly with mysidaceans and dolioles. The groups that did not have a clear association with environmental variables were the chaetognaths, pteropods, decapods and bryozoans.

Regarding the multivariate statistical result of sampling stations and months with respect to environmental variables (Fig. 4 B), a more heterogeneous arrangement of data was obtained with the formation of three clusters; the first one gathered most of the samples from Punta Gato station and was found to be associated with the Chla. The second cluster, related to SST, gathered the stations sampled during the warmest period of the year (July, August, September). The third grouping was associated with salinity and DO, comprising stations sampled during spring and autumn located in areas near the mouth of the Bay.

Live/dead ratio

The variation of live/dead zooplankton of copepods, decapods and chaetognaths showed fluctuations throughout the year, without significant monthly variability and the proportion of live zooplankton was always higher than dead organisms during the analyzed period (Fig. 5 A). Copepods (Fig. 5 B) showed high proportions of live organisms throughout the 2015 cycle, with March being the exception where live/dead proportions were similar. On the other hand, decapods and chaetognaths (Fig. 5 C and D) presented their highest percentages of live organisms during February, May and August, compared to April, September and November when the percentage of dead organisms was higher.

On the spatial scale (Fig. 6 A) the difference between live and dead was always significant (P < 0.05). The Punta Gato and Baja Seas stations had higher numbers of live organisms than dead ones; on the other hand, at the Palmita and Boca stations the situation was reversed. The three taxa analyzed showed the same pattern of survival on the spatial scale (Fig. 6 B, C and D). Copepods presented minimum mortalities at Punta Gato and Baja Seas stations (Fig. 6 B), while decapods and chaetognaths presented their highest mortalities at Boca station (Fig. 6 C and D).

At the taxon level, copepods maintained low mortality rates throughout the 2015 annual cycle. The maximum values of dead copepods were recorded during March (51%), while during the rest of the year the average was approximately 18%. Decapods and chaetognaths had the highest percentages of dead organisms during April (76% and 85%, respectively). The annual mortality average for these taxa was 32% for decapods and 33% in chaetognaths; however, the proportions of dead organisms increased during the second half of the year in both decapods and chaetognaths (Fig. 7).

Analysis between sampling stations showed that mortality percentages were minimal at the Punta Gato (9%) and Baja Seas (4%) stations. In contrast, Palmita (75%) and Boca (78%) had high percentages of dead organisms (Fig. 8). Copepods and decapods had the highest numbers of dead organisms at Boca station (74% and 96%, respectively), while chaetognaths had them at Palmita station (72%).

The sea temperature in Magdalena Bay had a well-defined seasonal pattern (Cervantes-Duarte et al. 2010), where an increase can be clearly observed during the second half of the year. The significant variability found in the SST may be caused by the interannual variability of the system itself, reinforced by the arrival of the El Niño event to the Mexican coast. Nevertheless, the difference in SST between the average minimum and maximum in 2015 was slightly higher in April (> 1.5°) and similar in August (> 0.5°C), compared to other periods without an El Niño event (Funes-Rodríguez et al. 2007). Salinity presented a stable trend during the first half of the year; however, an increase in the average was observed from August to October. This was due to the increase in solar irradiance during most of the second semester, attributable to the high temperature and evaporation, especially in the shallow stations; in addition to its relationship with the presence of water of subtropical origin from outside, which is warmer and saltier (Cervantes-Duarte et al. 2013). Dissolved oxygen (DO) showed significant changes related to the seasonal variation of SST. During the first half of the year, DO concentration increased in the cold season, while in the second half of the year it decreased as SST increased, being higher than 5 ml L^− 1 on average; therefore, it should not be a limiting factor in organisms, since hypoxia could occur under concentrations lower than 2 ml L^− 1 (Roman et al. 2019). The increase in oxygen concentration (late spring and early summer), could be related to the intensity of the winds, which allows ocean-atmosphere exchange, especially in the shallower seasons, as occurs in this season when the northwest winds are more intense (Obeso-Nieblas et al. 1999). The concentration of Chla, despite not showing significant differences throughout the period studied, showed an increase from late spring and early summer, similar to what has been reported in other studies (Cervantes-Duarte et al. 2007, 2010, 2012, 2013; Murillo-Murillo et al. 2013). Similarly, Chla maxima in the adjacent marine zone, presented this same temporal variation, related to upwelling events (Martínez-López and Verdugo-Díaz 2000). However, the Chla concentration was comparatively lower than reported in other studies (Cervantes-Duarte et al. 2010, 2013), probably because this research was conducted along the Bay coastline during neap tides and in an El Niño year. The highest Chla concentrations were observed in the shallowest and innermost portion of the Bay (Punta Gato), which coincides with the findings of different authors, probably due to the contribution of nutrients from waste discharges, resuspension of sediment rich in organic matter and the contribution of organic matter from mangrove forests, among others (Cervantes-Duarte et al. 2014; Cervantes-Duarte and García-Romero 2016; Jiménez-Quiroz et al. 2019).

Variability of zooplankton community structure

The effects of sea warming on zooplankton abundance in northwestern Mexico and Magdalena Bay are in the trend of decline since the 1980s (Palomares-García and Gómez-Gutiérrez 1996; Hernández-Trujillo et al. 2010; Jiménez-Quiroz et al. 2019), as similar values have been recorded in the most recent El Niño events (1997–1998; 2015–2016), with decreases of up to 25%, with respect to 1982–1983 (Palomares-García and Gómez-Gutiérrez 1996; López-Ibarra and Palomares-García 2006; Jiménez-Quiroz et al. 2019).

During El Niño 2015, 20% more taxonomic groups were found than reported by Hernández-Trujillo et al. (2010) for a relatively cold period; this increase in groups may be associated with the tropicalization of the ecosystem that has been reported in previous studies (Palomares-García and Gómez-Gutiérrez 1996; Cota-Meza et al. 1992; Jiménez-Rosenberg et al. 2007). On the other hand, the number of taxonomic groups is higher than that recorded during El Niño 1997–1998 (Hernández-Trujillo et al. 2010), although this is probably due to differences in sampling effort compared to this study.

During this research, no differences were found among the most abundant zooplankton taxa with respect to the historical reported for Magdalena Bay (Gómez-Gutiérrez et al. 2001; Hernández-Trujillo et al. 2010), for example copepods were the most abundant taxonomic group in the community, consistent with what was reported by Gómez-Gutiérrez et al. (2001) and Hernández-Trujillo et al. (2010).

On the other hand, the reduced abundance of zooplankton collected was probably due to the scarcity of phytoplankton reported by Jiménez-Quiroz et al. (2019) for the study area, as a consequence of the prolonged warming to which the bay was subjected. In addition, the mesh size was an important factor in determining the abundance found, which was lower than expected, collecting mesozooplankton and adult stages of zooplankton.

The warm sea conditions in MB were recorded from the beginning of 2015 until the end of 2015. As mentioned, the typical seasonal condition in Magdalena Bay was compounded by the concurrence of TB and El Niño 2015-16. As a consequence, throughout the annual cycle, sea temperature was found to be warmer than the historical reported for MB and the biological affectations and structural changes in marine communities demonstrated this (Jiménez-Quiroz et al. 2019). The highest zooplankton abundances were recorded in the innermost station of the Bay (Punta Gato), probably because at this site Chla concentrations were higher than in the rest of the oceanographic stations analyzed.

In MB the time series of specific abundance of copepods confirms them as the dominant group, even under atypical weather conditions such as those produced during El Niño events (Hernández-Trujillo et al. 2010) although the community structure has had important changes that when contrasted over time evidence hierarchical changes of predominance and, therefore, of resource utilization in the ecosystem (Jiménez-Quiroz et al. 2019).

In this context, copepods in the studied area showed increases in abundance during the first and second half of the year, possibly due to the increase in specific richness and the consequent morphological and physiological characteristics, in addition to the type of feeding. During El Niño 1982–1983 there was a seasonal replacement of Paracalanus parvus, during the first part of the year, by Acartia lilljeborgii and A. tonsa in the second part (Palomares-García and Gómez-Gutiérrez 1996). In 2015 there was no species turnover, and A. lilljeborgii dominated throughout the year (Alemany-Rodríguez 2019), associated with a warm environment that favored the permanence of the species. One aspect that supports this fact is the high fecundity of the species throughout the year (Palomares-García and De Silva-Dávila 2007).

The presence of salpids and jellyfish, associated with higher SST, is consistent with the biology of these groups, which have a wide tolerance in warm habitats (Gasca and Suárez-Morales 1996), likewise the presence of diplostracs and appendicularias occurred in waters with high Chla concentrations, probably due to their feeding habits. These groups are described (mostly, in the case of diplostracs) as herbivores, which may explain their distribution in areas with high Chla concentration, which can be taken as a proxy for areas of high phytoplankton cell density (Longhurst 1985; Bacescu and Petrescu 1999).

Statistical analysis of oceanographic stations with environmental variables correlated Punta Gato with Chla gradients, probably because this station has an associated mangrove area that may contribute to the greater contribution of nutrients in the form of dissolved organic matter to the marine environment (Cervantes-Duarte et al. 2014; Jiménez-Quiroz et al. 2019).

Live/dead ratio

We observed that the increase in TSS influenced the proportion of live and dead zooplankton, considering that this environmental variable is the one that prevalently affects all biological processes in the sea and becomes a disruptive element in the pelagic ecosystem.

The highest proportions of dead organisms coincided with the months where the lowest concentration of Chla was recorded. This indicates the close relationship between zooplankton and primary productivity in the study area, even when the taxonomic groups in question are not strictly herbivorous (Longhurst 1985).

Coastal upwellings were weak during 2015 off Magdalena Bay (Cervantes-Duarte et al. 2021). These upwellings constitute the main nutrient input to the bay (Zaytsev et al. 2003). The weakening of the upwellings may have been related to high air temperature and low wind strength (Zaba and Rudnick 2016; Gómez-Ocampo 2017).

The highest percentage of live zooplankton was observed inside the lagoon (Punta Gato) and at the Baja Seas station. The inner station presented particular conditions due to the contribution of nutrients from the residual discharges of the San Carlos estuary, resuspension of sediment rich in organic matter and the contribution of organic matter from the mangrove forests, among others (Cervantes-Duarte et al. 2014; Cervantes-Duarte and García-Romero 2016; Jiménez-Quiroz et al. 2019), which could be forming a "microhabitat" in this area that could favor the survival of the zooplankton community. In addition, Baja Seas is the area where there is an artificial food supply for fish farming, which, together with the excreta from the fish farming, contributes to the supply of nutrients and consequent enrichment of this area (Mangion et al. 2017).

The Palmita and Boca stations showed very high mortality percentages as a consequence of the oligotrophic conditions and stress generated in the lagoon by the joint action of the warming events and the weakening of the upwelling during 2015 in MB (Cervantes-Duarte and García-Romero 2016; Jiménez-Quiroz et al. 2019).

Copepods, having the lowest percentage of dead organisms throughout the study period in MB, showed their adaptive capacity to withstand thermal stress conditions more efficiently than other taxa of the zooplankton community (Elliott et al. 2010; Elliott and Tang 2011; Medellin-Mora 2016). This group maintained stable and high survival percentages throughout the year, presenting maximum survival rates both in the cold and warm seasons, which is due to the wide trophic diversity it presents, allowing it to take optimal advantage of the resources available in the environment (Kleppel et al. 1988; Gasca and Suárez-Morales 1996; Palomares-García et al. 2003).

Decapods and chaetognaths presented higher percentages of dead organisms, probably due to the unavailability of suitable prey and a lower capacity to survive the persistent warm conditions throughout the 2015 annual cycle. Chaetognaths are strictly carnivorous organisms (Cota-Meza et al. 1992) and therefore require the presence of potential prey and a high abundance of prey. However, López-Ibarra (2008) mentions a greater susceptibility of herbivorous organisms to El Niño conditions since carnivorous and omnivorous organisms have greater plasticity to compete for resources in pelagic environments.

The data obtained on the live/dead zooplankton ratio indicate that for the period studied it fluctuated significantly and that this ratio should be taken into account in the assessment of abundance by group, and not generalized due to the physiological capacity that each one of them has to adapt to environmental variability. However, it is an indicator of the live biomass that is captured in mesozooplankton tows and that is what is carrying out the energy transfer in the marine pelagic food web. It is also necessary to obtain these ratios from microzooplankton to have a closer estimate of the live/dead ratio and to have a proxy for non-predatory mortality of marine zooplankton.

Funding

This work was supported by grants SIP20195337, SIP20200168, SIP20210015, and SIP20220534 from Instituto Politécnico Nacional. Author Emilio Alejandro Alemany Rodríguez has received research support from CONACYT fellowship A200539.

Author Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Emilio Alejandro Alemany-Rodríguez and Sergio Hernández-Trujillo. The first draft of the manuscript was written by Emilio Alejandro Alemany-Rodríguez and Sergio Hernández-Trujillo commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Ethics approval

Ethics approval was not required for this research.

Consent to participate.

All the authors participated in this article.

Consent for publication

All the authors were informed and agreed to the study.

Competing interests

The authors declare no competing interests.

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Table 1. Composition, relative abundance and frequency of occurrence of zooplankton in Magdalena Bay during 2015.

Taxonomic level	Group name	Relative abundance RA (%)	Ocurrence O (%)
Class	Copepoda	37.6	97.73
Order	Decapoda	19.5	97.73
Superorder	Diplostraca	10.16	90.91
Phylum	Chaetognatha	8.04	97.73
Gigaclass	Actinopterygii (fish eggs)	6.78	97.73
Class	Appendicularia	4.12	91.25
Infraorder	Brachyura	3.09	84.09
Order	Doliolida	1.96	65.91
Subclass	Cirripedia	1.44	45.45
Order	Salpida	1.21	38.64
Order	Pteropoda	1.05	59.09
Order	Stomatopoda	0.96	29.09
Class	Hydrozoa	0.71	47.73
Order	Amphipoda	0.63	70.45
Order	Siphonophorae	0.51	61.36
Gigaclass	Actinopterygii (larvae)	0.42	81.82
Order	Neogastropoda	0.4	34.09
Order	Ophiurida	0.33	15.91
Class	Polychaeta	0.28	45.45
Order	Mysida	0.21	36.36
Order	Euphausiacea	0.12	38.64
Phylum	Bryozoa	0.11	9.09
Phylum	Nematoda	0.08	2.27
	Nauplii	0.08	47.73
Class	Ostracoda	0.06	61.36
Class	Bivalvia	0.04	6.82
Order	Isopoda	0.04	27.27
Order	Leptothecata	0.02	15.91
Phylum	Ctenophora	0.01	2.27
Subclass	Coleoidea	0.01	2.27
Order	Littorinomorpha	0.01	2.27
Order	Cumacea	0.01	4.55
Phylum	Echinodermata	0.01	4.55

Table 2. Axis eigenvalues and explained variance (%) from a canonical correspondence analysis using zooplankton groups, SST, Salinity, DO and Chla in Bahía Magdalena during 2015. Asterisks represents p < 0.05

Metric	Axis 1	Axis 2	Axis 3
Eigenvalue	0.321	0.101	0.895
Explained variance (%)	17.4	3.9	1.17
Accumulated variance (%)	17.4	21.3	22.47
Pearson correlation	0.817	0.709	0.31
Correlation values
Sea surface temperature (SST)	0.842*	0.421	0.297
Salinity	-0.413	-0.617	-0.133
Dissolved Oxygen (DO)	-0.308	-0.206	0.024
Chlorophyll a (Chla)	-0.76*	0.442	0.003

Non-predatory mortality assessment of zooplankton in Magdalena Bay, Mexico, during El Niño 2015.

Status:

Journal Publication

Version 1

Abstract

Figures

Introduction

Materials and methods.

Results

Zooplankton Community Structure

Relationship between taxonomic groups and environmental variables

Live/dead ratio

Discussion

Variability of zooplankton community structure

Live/dead ratio

Declarations

References

Tables

Status:

Journal Publication

Version 1