IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 9, September 2015. www.ijiset.com ISSN 2348 – 7968 Planktonic Abundance and Diversity In , State,

Antai, Ekpo Eyo* and Joseph, Akaninyene Paul Institute of Oceanography, University of , Calabar, Nigeria

ABSTRACTS Studies on the abundance and diversity of plankton (phytoplankton and zooplankton) in Great Kwa River, South Eastern Nigeria, was undertaken bi-weekly for 3 months from July to September 2013. Samples were collected from two stations based on human activities at these stations. The Objective of the study was to determine the abundance and Distribution of various planktonic groups across the sampling stations. Samples were collected using the pour through method. A total of 26 species and 574 phytoplankton individuals belonging to 4 families were observed during the study. The families represented were Bacillariophyceae 49.83%, Chlorophyceae 21.25%, Chrysophyceae 16.55 and Cyanophyceae 12.37. A total of 23 species and 344 Zooplankton individuals belonging to 5 taxonomic groups were also identified during the study. The groups represented were Rotifera 28.49%, Arthropoda 24.71%, Palaemonidae 16.86%, Ciliophora 15.12% and Annelida 14.82%. This study showed diversity in plankton distribution in Great Kwa River and their possible impacts on the local fisheries is discussed

KEY WORDS: Phytoplankton, Zooplankton, Abundance, Diversity, Great Kwa River, Calabar.

*Corresponding Author. Email: ekpo.eyoa @yahoo.com

INTRODUCTION

Plankton is any drifting organisms that inhabit the pelagic zone of aquatic ecosystems and they serve as the food base that supports aquatic life. The phytoplankton are the primary producers which serves as food majorly for zooplankton which in turn serves as an important source of food to crustaceans and fish (Thurman, 1997). They therefore, serve as a major source of organic carbon in rivers and may represent an important source of oxygen in low-gradient aquatic ecosystem. An assessment of plankton community and abundance will enhance our understanding of biological productivity and fish population dynamics (Williams 1962, Fagade and Olaniyan 1974, Abohweyere 1990 and Onyema

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Although phytoplankton distribution and abundance are largely influenced by the light and nutrient, alteration of their natural environment by man can greatly distort this equilibrium. These may explain why plankters are used as bioindicators to monitor aquatic pollution. Zooplankton is ecologically an important group of aquatic organisms that occupy a wide range of habitats. They constitute essential biotic components which influences the efficiency of an aquatic ecosystem such as energy flow through various trophic interactions (Park and Shin, 2007). Copepods have been shown to be the major link between phytoplankton and first level carnivores while arrow worms are the common carnivores in zooplankton (Tse et al., 2007).

The species composition, diversity, biomass and season of maximum abundance of zooplanktonic organisms differ in water bodies (FAO, 2006). The study is designed to estimate the abundance of various planktonic groups as well as to assess the variations in abundance and distribution of various planktonic groups across the sampling stations.

MATERIALS AND METHODS

Study Area and Sample Collection The study was undertaken at 2 locations at the Great kwa River. Great Kwa River is one of the main tributaries of Cross River Estuary in , Nigeria. It discharges into the estuary at latitude 4.450N and longitude 8.200E South East Nigeria. Substratum here is covered with sand and clay with an average depth of 0.1m. It is slow flowing and has low to medium transparency. It is located in the thick forested belt of South-East Nigeria and transverses through mangrove to fresh water swamp. The fringes of the river are dominated by the Nypa fruticans that has displaced mangrove plants, elephant grasses (Pennisetun purpureun), palm trees (Elias guineesis) and fan palm (Hyphaene petersiana) supporting an incredible array of animal life. The swampy region is greatly influenced by physical conditions as the tides continually exhibit fluctuations. The climate is governed by two seasons the wet (April to October) and the dry (November to March)

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IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 9, September 2015. www.ijiset.com ISSN 2348 – 7968 Samples were collected from 2 stations (Fig. 1) along Great Kwa River, a tributary of Cross River estuary. The stations are impacted by human activities. Station 1 (Esuk Atu) has low transparency and the substratum is mainly sandy clay. Station 2 (Idundu) has medium transparency with substratum of coarse sand and clay.

Samplings were undertaken fortnightly in the mornings from July to September 2013 by pour through method. Twenty litres of the water sample were collected just beneath the surface and poured through 55µm mesh size plankton net. These were repeated 5 time to add up to 100 litres. The planktons were immediately fixed with 5% formalin solution in 50 ml sampling bottle and transported to the laboratory for analysis and identification. The samples were concentrated to 10mls to enable analysis.

One ml of the preserved sample was taken using a pipette. This was place into Sedgwick- rafter counting chamber and viewed under different magnifications (x100 and x400) using a light binocular microscope (Nikon 400 binocular microscope). These were done in triplicates. The plankton were identified and sorted into different taxonomical groups with the aid of appropriate identification schemes (Mann 2000, Prasad 2000, Castro and Huber 2005).

Fig 1: Map of Great Kwa River Showing the Sampling Stations

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Ecological diversity indices In this study, three ecological statistics were used to obtain the estimation of species diversity, species richness and species evenness. Margalef’s Index (d): is a measure of species richness and is expressed as: d = (S – 1)/InN Where; d = Species richness index S = Number of species in the sample N = Number of individuals in the samples (Margalef, 1951)

Shannon and Weiner’s Index (H): is a measure of species abundance and evenness and is expressed as:

H = (Ni/N log2 Ni/N)

Where;∑ N = The total number of individual in the sample.

Ni = The total number of individuals of species ith in the sample (Shannon and Weiner’s, 1949).

Species Equitability or Evenness (E): is determined by the equation: E =H/In S Where; H = Shannon and Weiner’s index. S = Number of species in samples (Pielou, 1966).

RESULTS AND DISCISSION Species Abundance, Diversity Index and Composition of Phytoplankton The species composition and abundance of the various Phytoplankton taxa encountered at the 2 sampling stations is presented in Table 1.

A total of 26 species and 574 phytoplankton individuals belonging to 4 families were observed during the study. The most abundant Phytoplankton species was Navicula petersenni (39 individuals), followed by Rhizosolena stiliformis (36 individuals) and then Cyclotella comta (35 individuals). Also, the least abundant Phytoplankton species was

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IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 9, September 2015. www.ijiset.com ISSN 2348 – 7968 Micrasterias sp. (8 individuals), followed by Pinnularia borealis (11 individuals) and then Coelosphaelium sp. (13 individuals) (Fig 2).

The families represented were Bacillariophyceae, Cyanophyceae, Chlorophyceae and Chrysophyceae. Bacillariophyceae family was the most abundant, having 286 individuals (49.82%), followed by Chlorophyceae which had 122 individuals (21.25%), Chrysophyceae with 95 individuals (16.55%) and Cyanophyceae, having only 71 individuals and a relative abundance of 12.38% (Figs 3 and 4). Diatom dominance of the phytoplankton waters within the region has been reported in other studies (Akpan 1997, Chinda and Braide 2004, Ekwu and Sikoki 2006 and Essien-Ibok 2013). Contrary, the dominance of Chlorophyta has been reported in Bonny River (Ajuonu et al 2011). Dimowo (2013) reported the dominance of Cyanophyta and an absesence of diatom in River Ogun. The high number of diatoms notice in this study may not be unrelated to high concentrations of silicate in the Cross River water system. Akapn (1997) reported a strong correlation between silicate and diatom abundance in the waters of Cross River. Commonly, in an aquatic system where there is no heavy nutrient inputs possibly from run-off or human inputs, Bacillariophyceae are usually the predominant, but when nutrient levels is high such that eutrophication occurs, then the Chlorophyceae could become more abundant than Bacillariophyceae (Akin-Oriola, 2003). The high plankton diversity from the study will support fishery in Great kwa River and the adjoining Cross River Estuary. Phytoplankton community structure gives a good evaluation of the stability of aquatic ecosystem and provides a veritable tool for the assessment of biological activities.

Table 1: Species composition and Abundance of Phytoplankton in the Study Area

S/N Phytoplankton families/ Station 1 Station 2 Total species Species No %RO No No %RO Bacillariophyceae 1 Skeletonema costatum 11 3.82 14 4.89 25 4.36 2 Rhizosolena stiliformis 20 6.94 16 5.59 36 6.27 3 Bidulphia sinensis 12 4.17 8 2.79 20 3.48 4 Coscinodiscus radiates 12 4.17 5 1.75 17 2.96 5 Cyclotella comta 21 7.29 14 4.89 35 6.09 6 Melosira granulate 13 4.51 4 1.39 17 2.96

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7 Navicula patersenni 18 6.25 21 7.34 39 6.79 8 Tabellaria fenestrate 12 4.17 22 7.34 34 5.92 9 Gyrosigma sp. 7 2.43 9 3.15 16 2.78 10 Cymbella sp. 8 2.78 7 2.45 15 2.61 11 Pinnularia borealis 8 2.78 3 1.05 11 1.92 12 Surrirela ovalis 6 2.08 15 5.24 21 3.66 286 49.8 Cyanophyceae 13 Lyngbya contorta 7 2.43 13 4.55 20 3.48 14 Oscillatoria rubiscens 8 2.78 14 4.89 22 3.83 15 Coelosphaelium sp. 11 3.82 2 0.69 13 2.26 16 Microcystis acrugiriosa 6 2.08 10 3.49 16 2.78 71 12.38 Chlorophyceae 17 Botryococcus boryanum 11 3.82 22 7.69 33 5.75 18 Tetraspora lubrica 7 2.43 10 3.49 17 2.96 19 Thalassomonas minima 8 2.78 8 2.79 16 2.78 20 Closterium sp. 10 3.47 8 3.49 18 3.14 21 Volvox aurus 16 5.55 14 4.89 30 5.23 22 Micrasterias sp. 7 2.43 1 0.35 8 1.39 122 21.25 Chrysophyceae 23 Dinobryon bavaricum 12 4.17 15 5.24 27 4.70 24 Synura sp. 9 3.13 12 4.19 21 3.66 25 Asterionella sp. 9 3.13 12 4.19 21 3.66 26 Crystochrisis sp. 19 6.59 7 2.45 6 4.53 95 16.55 Total Abundance 288 100 286 99.9 574 100 Shannon weinner index 4.53 4.48 Margalef index 4.41 4.42 Pielou index (Evenness) 1.39 1.37

In terms of diversity index, Shannon Weinner diversity index were 4.53 and 4.48, Margalef Index, 4.41 and 4.42 and Pielou diversity index, 1.39 and 1.37 in Stations 1 and 2 respectively (Table 1).

The Great kwa River is rich in phytoplankton based on the assessment of abundance and

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IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 9, September 2015. www.ijiset.com ISSN 2348 – 7968 diversity. This river should be protected from anthropogenic activities since this will distort the nutrient balance and not suitable for the growth of plankton thereby impacting on biological productivity including fish recruitment and other aquatic lives.

Table 2: Species composition and Abundance of Zoooplankton in the Study Area

S/ Zooplankton families/species Station 1 Station 2 Total species N No %Ro No %Ro No %Ro Rotifera 1 Asplancha priodonta 12 7.02 7 4.05 19 5.52 2 Asplancha girodi 3 1.75 7 4.05 10 2.91 3 Euchalarius sp. 9 5.26 9 5.20 18 5.23 4 Squatinella rustrum 4 2.34 4 2.31 8 2.33 5 Phlodina sp. 9 5.26 11 6.36 20 5.81 6 Keratella eochlearis 8 4.68 6 3.47 14 4.07 7 Conochilus unicornis 6 3.51 3 1.73 9 2.62 98 28.49 Arthropoda(Crustacea) 8 Leptodora sp. 9 5.26 5 2.89 14 4.07 9 Calanus calanus 4 2.34 8 4.62 12 3.49 10 Calanus finmarchirus 5 2.92 9 5.20 14 4.07 11 Euchalanus elongates 8 4.68 7 4.05 15 4.36 12 Pseudocalanus elongates 6 3.51 - - 6 1.74 13 Oithona rana 6 3.51 13 7.51 19 5.52 14 Limnocalanus macrurus 2 1.17 3 1.37 5 1.45 85 24.70 Ciliophora (Ciliata) 15 Strambildium strobilus 7 4.09 12 6.94 9 5.52 16 Strambildium conicum 7 4.09 3 1.73 10 2.91 17 Leptotintinnis peliucidus 4 2.34 5 2.89 9 2.62 18 Stensmella nivalis 10 5.85 4 2.31 14 4.07 52 15.12 Annelida (Polychaeta) 19 Neceis deversicolor 12 7.02 11 6.36 23 6.68 20 Autolysis edwardsi 13 7.60 15 8.67 28 8.14 51 14.82 Palaemonidae (Shrimp) 21 Macrobrachium vollenvohenii 12 7.02 12 6.94 24 6.98 22 Macrobrachium Macrobrachion 10 5.85 12 6.94 2 6.39 23 Macrobrachium equidens 5 2.92 7 4.05 12 3.49 58 16.86 Total Abundance 171 100 173 99.9 344 99.9 Shannon Weinner index 3.85 3.90 Margalef Index 4.28 4.08 Pielou index (Evenness) 1.23 1.26

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45

40

35

30

25

20

15 Numerical Abundance Numerical 10

5

0 Synura sp. Volvox aurusVolvox Cymbrellasp. Gyrosigma sp Closterium sp. Surrirelaovalis Asterionella sp. Micrasteriassp. Crystochrisis sp. Cyclotellacomta Lyngbyacontorta Bidulphia sinensis Tetraspora lubrica Melosira granulata Melosira Pinnulariaborealis Coelosphaeliumsp. Naviculapetersenni Tabellariafenestrata Dinobryonbavaricum Oscillatoriarubiscens Rhizosolenastiliformis Microcystisacrugiriosa Skeletonema costatum Coscinodiscus radiatus Thalassomonas minima Botryococcus boryanum Botryococcus Phytoplankton species

Fig 2: Phytoplankton species abundance in the study area

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150

Numerical Aabundance 100

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0 Bacillariophyceae Cyanophyceae Chlorophyceae Chrysophyceae Phytoplankton families

Fig 3: Phytoplankton taxonomic abundance in the study area

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Chrysophyceae 17%

Bacillariophyceae 50% Chlorophyceae 21%

Cyanophyceae 12%

Fig 4: Relative Abundance of the Phytoplankton Families in the Study area

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15

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Numerical Abundance Numerical 5

0 Philodina sp Oithona rana Leptodorasp. Euchalanus sp.Euchalanus Asplancha girodiAsplancha Calanus calanus Calanus Nereis diversicolor Stensmellanavalis Autolytus edwardsi Squatinellarustrum Keratella eochlearisKeratella Asplancha priodontaAsplancha Conochilusunicornis Calanus finmarchirusCalanus Strombilidiumstrobilus Strombilidiumconicum Euchalamuselongatus Leptotintinnispeliucidus Limnocalanus macrunusLimnocalanus Macrobrachium equidens Pseudocalamus elongatusPseudocalamus Macrobrachium vollenvohenii Macrobrachium macrobrachion Zooplankton species

Fig 5: Zooplankton species abundance in the study area

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120

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80

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40 Numerical Aabundance

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0 Rotifera Arthropoda Ciliophora Annelida Palaemonidae Zooplankton family

Fig 6 : Zooplankton taxonomic abundance in the study area

Palaemonidae 17% Rotifera 28%

Annelida 15%

Ciliophora Arthropoda 15% 25%

Fig 7: Relative Abundance of the Zooplankton taxonomic groups in the study area

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IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 9, September 2015. www.ijiset.com ISSN 2348 – 7968 Species Abundance, Diversity Index and Composition of Zooplankton Summary of the species composition and abundance of the various Zooplankton taxa encountered at the different sampling stations is presented in Table 2. A total of 23 species and 344 Zooplankton individuals belonging to 5 phyla were observed during the study. Zooplankton species abundance is presented in Fig 5.

The results obtained showed the relative abundance of zooplankton followed a decreasing sequence of Rotifera 28.49% > Arthropoda 24.70 > Palaemonidae 16.86 > Ciliophora 15.12% > Annelida 14.82%. Rotifera was the most abundant phylum, having 98 individuals and a relative abundance of 28.49%, followed by Arthropoda which had 85 individuals and a relative abundance of 24.70%. Palaemonidae had a total numerical abundance of 58 individuals and a relative abundance of 16.86%. Ciliophora had 52 individual and a relative abundance of 15.12%. The least represented Zooplankton phylum was Annelida, having only 51 individuals and a relative abundance of 14.82% (Figs 6 and 7).

In terms of zooplankton diversity index, Shannon Weinner diversity index was 3.85 and 3.90, Margalef index of 4.28 and 4.08 and Pielou diversity index of 1.23 and 1.26 at Stations 1 and 2 respectively (Table 2).

The dominance Rotifera in the study is similar to the report of Agouru and Audu (2012), Ajuonu et al. (2011) reported Copepods as the most abundant Zooplankton in Bonny River. Kibria et al. (1997), Yakubu et al. (1998) and Dimowo also reported that dominance of Cladocera. This variation could be due to differences in study area, period, phytoplankton types and availability, nutrients availability, diversity, biomass and the season of maximum abundance of zooplanktonic organisms differ in water bodies (FAO, 2006).

Great Kwa River is a rich ecological ecosystem with high plankton diversity that can sustain fishery development. A study of primary and secondary productivity in this water body will give a better understanding of the trophodynamic within the system. However this can be affected by anthropogenic input such as industrial and municipal effluents that may likely be discharged into this River

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