ACKNOWLEGMENT…………………………………………………………… i
LIST OF TABLE……………………………………………………………..…….ii-iii
LIST OF FIGURES…………………………………………………………….…..iv-x
THESIS ABSTRACT………………………………………………………………xi-xii
CHAPTER # 1
INTRODUCTION OF DISSERTATION…………………………………………1
INTRODUCTION...... 2
AIMS AND OBJECTIVES OF STUDY………………………………………...6
STRUCTURE OF THESIS……...... 6-7
REFERENCES...... 9-14
CHAPTER # 2
ENVIRONMENTAL EFFECTS ON ZOOPLANKTONS COMMUNITY DYNAMICS AND ABUNDANCE IN COASTAL WATERS, MANORA, PAKISTAN...... 8
ABSTRACT ...... 9
1. INTRODUCTION ...... 10-12
2. MATERIALS & METHODS...... 13-18
3. RESULTS...... 19-47
3.1. VARIATIONS IN ENVIRONMENTAL PARAMETERS 3.2 MESOZOOPLANKTON DIVERSITY AND ABUNDANCE 3.3. EFFECTS OF ENVIRONMENTAL VARIABLES ON MZ 3.4. MESOZOOPLANKTONS AND CHLOROPHYLL RELATION 4. DISCUSSION ...... 48-51 5. CONCLUSION………………………………………………………………..…52 CHAPTER 3
COPEPODS COMMMUNITY STRUCTURE IN SHALLOW, MANGROVE WATERS IN NORTHERN ARABIAN SEA ...... 53
ABSTRACT ...... 54
1. INTRODUCTION ……………………………………...... 55-57 2. MATERIALS & METHODS...... 58-60 3. RESULTS...... 61-108 3.1 SPECIES DISTRIBUTION AND DENSITY 3.2 SEASONAL VARIATION IN ABUNDANCE OF COPRPODS 3.3 GENUS ASSOCIATION BETWEEN THE STATIONS 4. DISCUSSION ...... 109-113 5. CONCLUSION…………………………………………………………...114
CHAPTER 4
ANNUAL AND TIDAL INDUCED CHANGES IN NUTRIENT ENERGY AND ITS EFFECT ON ZOOPLANKTON ABUNDANCE AND PHYTOPLANKTON BIOMASS...... …….115 ABSTRACT...... 116
1. INTRODUCTION…...... 118-119
2. MATERIALS & METHODS...... 120-123
3. RESULTS...... 124-148
3.1. ANNUAL NUTRIENT DISTRIBUTION
3.2. COMPOSITION OF ZOOPLANKTON FEEDING GUILDS IN MANGROVE FOREST
3.3. AUTOTROPHIC AND HETEROTROPHIC BIOMASS COUPLING
3.4. EFFECT OF NUTRIENTS ON PLANKTON
3.5. MAGROVE TIDAL CYCLE
4. DISCUSSION...... 149-153
5. CONCLUSION…………………………………………………………...154 CHAPTER 5
DISSERTATION DISCUSSION AND FUTURE RECOMMENDATION…155
GENERAL DISCUSSION ………………………………………………………156-160
FUTURE RECOMMENDATIONS……………………………………………...161
REFERENCES ...... 162-195
ACKNOWLEDGEMENTS
Without the acknowledgments this dissertation would not be encourage. First and foremost especial thanks to ALLAH who made me to achieve this goal. Best regards I would like to pay my mentor and research supervisor, Dr. Sumera Farooq, Who was a sign of inspiration for me. Without her encouragement the dissertation would not be completed as it is. People who supported me guided me throughout the journey of this research, who contributed their efforts morally and professionally are appreciable, I would like to give special thanks to them for their generous sharing.
I would like to pay attribute to the Centre of Excellence in Marine Biology for financial support and for their encouragement. All the respected teachers of the CEMB. I would pay best wishes to the lab attendants for their hard work during and after sampling.
Thanks to all of my research colleagues who supported me during the course of my research, who appreciated me to reach the goal. I really pay especial gratitude to the director of CEMB for her kindness and support.
I extremely express thanks to my research co supervisor Dr. P.J.A Siddiqui who was very supportive to me till the completion of dissertation.
The most recognizable support, love, care and sacrifices from my family who provided me good environment and financial support to complete my task. Whatever the matter was the whole family, my child and husband supported me for being a scientist.
To sum up I would like to pay heartily thanks to all the people who raise my spirits from day till the completion of dissertation.
MUBEEN ARA
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Chapter 2.
Table 1 Physical and biological parameters ranges and annual mean values from mangrove and coastal stations……………………………………….…20
Table 2 Relative abundance (%) of different studied groups of MZ (excluding Copepods) in surface and 5m waters (in parenthesis). *Marine planktonic worms include all identified worms…………….………………………28
Table 3 Comparison of Total mean abundance (Ind.m-3) and % Occurrence of mesozooplankton at four stations……….………………………………29
Table 4 Comparison of total copepods mean density at surface and 5m waters (Ind. m-3) from four stations……………………………………………30
Table 5 Linear regression analysis and one-way ANOVA (P < 0.05) for zooplankton groups with four predictor variables at all four stations………………..41
Chapter 3.
Table 1 Comparison of copepods diversity index, evenness and richness at all stations……………………………………………………………..……62
Table 2 Group mean abundance and vertical distribution of the copepods at all stations during September 12 to September 13………….……………..66
Table 3 Total abundance of species Ind.m-3 at all stations with their occurrence frequency (OF %) and relative frequency (RA %)……………………...99
Table 4a Species wise seasonal fluctuation of order calanoida during PRE (pre- monsoon), SWM (southwest monsoon), POM (post monsoon) and NEM (northeast monsoon)………………………………….……………102-103
Table 4b Species wise seasonal fluctuation of order cyclopoida and harpacticoida during all four seasons……………………………………………….....104
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Table 5. Linear regression analysis and one-way ANOVA (P < 0.05) between stations for copepods species……………...……………………...…....105
Chapter 4.
Table 1. Regression analysis and one way one way ANOVA (P < 0.05) among stations with respect to the nutrient concentration…………..…………125
Table 2. Regression analysis and one way ANOVA (P < 0.05) for the nutrient concentration with respect to phytoplankton and zooplankton biomass. And total zooplankton abundance with Phytoplankton biomass………………………………………………….…………….135
Table 3. Regression analysis and ANOVA (P < 0.05) between tidal heights and different hydro biological factors…………….………………………139
Table 4. Regression analysis and ANOVA (P < 0.05) for nutrient concentration with respect to phytoplankton and zooplankton biomass during a complete tidal cycle..…………………………………………………………...139
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Chapter 1
Figure 1 World Ocean data base 2009, geographical distribution of (a) Phytoplankton (37,461 casts). (b) Zooplanktons (44,303 casts) White Point representing the northern Arabian Sea clutches of planktons. (Baranova et al 2009)………….………………………………....…...... 4
Chapter 2
Figure 1 Study site map showing collection sites in side Manora channel and outside Manora channel……………………..……………………...... 14
Figure 2 Sampling sites. HS (Harbor station), OC (Open Ocean) and mangrove forest stations HBM (Himalaya backwater mangrove) and SBM (Sandspit backwater mangrove)……………….………...………….……….……15
Figure 3 Annual fluctuation of physicochemical parameters (Temperature and Salinity) at all studied sites, HS and OC and two Mangrove sites HBM and SBM…………………………………………………….…………21
Figure 4. Annual variation in pH and dissolved oxygen (DO, mg-L-1) at HS, OC, HBM and SBM……………………………..……………………….….22
Figure 5. Annual variation between transparency (m) and TSS (mg-L-1) at HS, OC and mangrove sites HBM and SBM……………………………..……..23
Figure 6 Comparison of Annual variation in phytoplankton biomass (Chl a) between HS and OC and mangrove forests, HBM and SBM……….....24
Figure 7 Seasonal Shannon-Wiener Div ersity Index (Hˈ) and species richness (d) at HS, OC, HBM and SBM……………………………………………….31
Figure 8. Mean density (Ind. m-3) of the MZ community groups at studied stations during September and October (2012) at surface and 5m depth...... …..32
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Figure 9. Mean density (Ind. m-3) of the MZ community groups at studied stations during November and December (2012) at surface and 5m depth…….33
Figure 10. Mean density (Ind. m-3) of the MZ community groups at studied stations during January and February (2013) at surface and 5m depth………...34
Figure 11. Mean density (Ind. m-3) of the MZ community groups at studied stations during March and April (2013) at surface and 5m depth………………35
Figure 12. Mean density (Ind. m-3) of the MZ community groups at studied stations during Mary and June (2013) at surface and 5m depth………………...36
Figure 13. Mean density (Ind. m-3) of the MZ community groups at studied stations during July and August (2013) at surface and 5m depth………….……37
Figure 14. Mean density of the MZ community groups at studied stations during September (2013) at surface and 5m (Ind. m-3) depth………….………38
Figure 15. Comparison of copepods and mesozooplankton (MZ) annual % of occurrence at HS, OC, HBM amd SBM………………………….……38
Figure 16. Variation in total abundance (Ind-m-3) within MZ and copepods……...39
Figure 17. Comparitive abundance of MZ (Ind-m-3) at HS, OC, HBM and SBM....39
Figure 18. Results of Bray-Curtis cluster analysis among MZ groups showing similarity in abundance at HS and OC……………………....…………42
Figure 19. Consequences of Bray-Curtis cluster analysis of MZ groups showing similarity in abundance at HBM and SBM……….…………...……….43
Figure 20. Mesozooplankton similarity between stations based on Bray-Curtis similarity matrix………………………………………………………..44
Figure 21. MDS ordination based on MZ abundance and monsoon season showing 80% resemblance between SWM and NEM at HS, OC and mangrove stations HBM and SBM………………………………………….……44
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Figure 22. (a) MDS ordination based on seasonal distribution and similarities between the stations in terms of MZ abundance at 4 stations during 4 monsoonal seasons (b) close view………………………………..…....45
Figure 23. Comparative variation in zooplankton total mean abundance (Ind. m-3) with Phytoplankton biomass (Chl a mg m-3)…………………………..47
Chapter 3.
Figure 1. Comparison of occurrence (%) of the four orders of copepods……...... 61
Figure 2. Variation in total average abundance (Ind-m-3) of 19 genus in 13 families of the order calanoida……………………………..…………………..64
Figure 3. Average abundance of (Ind-m-3) 4 cyclopoids families and 5 genus…..65
Figure 4. Average abundance (Ind-m-3) of the families and genus of harpacticoida and Monstrillloida……………………………………………………..65
Figure 5. Annual vertical varition in mean density (Ind. m-3) of two species of the family calanidae in surface and 5mdepth at all stations………………..71
Figure 6. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Paracalanidae in surface and 5m depth at all stations…….…72
Figure 7. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Paracalanidae in surface and 5m depth at all stations…….….73
Figure 8a. Annual vertical distribution and mean abundance (Ind. m-3) of the Eucalanus bungii of family Eucalanidae in surface and 5m depth at all stations…….…73
Figure 8b. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Eucalanidae at all stations in surface and 5m depth……....…74
Figure 9. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Rhincalanidae in surface and 5m depth at all stations……….75
Figure 10. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Clausocalanidae at all stations in surface and 5m depth…….75 vi
Figure 11. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Euchaetidae in surface and 5m depth at all stations………….76
Figure 12a. Annual vertical distribution and mean abundance (Ind. m-3) of the 4 species of family Centropagidae at all stations in surface and 5m depth…….….…....77
Figure 12b. Annual vertical distribution and mean abundance (Ind. m-3) of the 4 species of family Centropagidae at all stations in surface and 5m depth……..…....78
Figure 13. Annual vertical distribution and mean abundance (Ind. m-3) of the 4 species of family Pseudodiaptomidae at all stations in surface and 5m depth.……79
Figure 14. Annual vertical distribution and mean abundance (Ind. m-3) of the 4 species of family Temoridae at four stations in surface and 5m depth……………82
Figure 15. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Candaciidae at all stations in surface and 5m depth…………83
Figure 16a. Annual vertical distribution and mean abundance (Ind. m-3) of the 3 species of the genus Calanopia family Pontellidae at all stations in surface and 5m depth………………..…………………………………………84
Figure 16b. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Pontellidae at all stations in surface and 5m depth……….…85
Figure 17. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Pontellidae at all stations in surface and 5m depth………….86
Figure 18. Annual vertical distribution and mean abundance (Ind. m-3) of Tortanus barbatus of family Tortanidae in surface and 5m depth at all four stations.86
Figure 19a. Annual mean abundance (Ind. m-3) and vertical distribution of the genus Oithona of family Oithonidae (order: cyclopoida) in surface and 5m depth at all stations……………………………………………………...……89
Figure 19b. Annual mean abundance (Ind. m-3) and vertical distribution of the genus Oithona of family Oithonidae (order: cyclopoida) in surface and 5m depth at all stations………………………………………………………..……….90 vii
Figure 20. Annual mean abundance (Ind. m-3) and vertical distribution of the genus Oncaea of the family Oncaeidae (order: cyclopoida) in surface and 5m depth at all stations…………………………………………….…….….91
Figure 21. Annual mean abundance (Ind. m-3) and vertical distribution of the family Sapphirinidae (order: cyclopoida) in surface and 5m depth at all stations....92
Figure 22. Annual mean abundance (Ind. m-3) and vertical distribution of the order Corycaeidae in surface and 5m depth at all stations……………….…....93
Figure 23. Annual mean abundance (Ind. m-3) and vertical distribution of the order Harpacticoida in surface and 5m depth at all stations…………..……….95
Figure 24 Annual mean abundance (Ind. m-3) and vertical distribution of the order Monstilloida in surface and 5m depth at all stations……………………97
Figure 25. Mean density (Ind.m-3) of copepod taxa in surface and 5m depth at all stations from September 12 to September 13………………………….100
Figure 26. Seasonal distribution and density (Ind.m-3) of three orders and total copepods during monsoon seasons……………………………………101
Figure 27. Cluster analysis based on Bray-Curtis similarity matrix calculated through monthly and seasonal density of copepods at two non-mangrove sites (HS and OC)……………………………………………………………….107
Figure 28. Cluster analysis based on Bray-Curtis similarity matrix calculated through monthly and seasonal density of copepods at two non-mangrove sites (HBM and SBM)……………………………………………..……...108
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Chapter 4.
Figure 1. Tidal chart showing tidal height variation and time during complete tidal cycle…………………………………………………………………………...121
Figure 2. Annual variations (September 2012- September 2013) in nutrients concentration at HS and OC………………………………………………………………….126
Figure 3. Annual variations (September 2012- September 2013) in nutrients concentration at HBM and SBM…………………………………………………………..….127
Figure 4. September 12 to September 13 percent variation in feeding groups of zooplankton in mangrove waters HBM………………………………...130
Figure 5. September 12 to September 13 percent variation in feeding groups of zooplankton in mangrove waters SBM………………………………...131
Figure 6. Percentage composition of zooplankton feeding guilds at HBM and SBM...... 132
Figure 7. Yearly distribution of zooplankton and phytoplankton biomass at non-mangrove stations HS and OC……………………………………………..…………….134
Figure 8. Yearly distribution of zooplankton and phytoplankton biomass in mangroves forest at station HBM and SBM………………………………………………134
Figure 9. Temperature variation at four tides during a complete tidal cycle…………...136
Figure 10. Salinity change at LT, HT and MT during a complete tidal cycle……………137
Figure 11. Tidal variation in pH during a complete tidal cycle. ……………………….137
Figure 12. DO variation during complete tidal cycle……………………………………..138
Figure 13. TSS and transparency relation at all four tides of a complete tidal cycle……...138
Figure 14. Tidal variation in zooplankton and phytoplankton biomass coupling…………140
Figure 15. Distribution of nutrient concentration at all four tides during a complete tidal cycle………………………………………………………………………..…141
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Figure 16. Percentage composition of zooplankton during LTd, HT, MT and LTn……..142
Figure 17. MZ group abundance (Ind-m-3) during Tidal cycle…………………………..143
Figure 18. Functional group distribution during tidal cycle. (a) Feeding group composition at LTd (b) feeding group composition at HT (c) feeding group composition at MT (d) feeding group composition at LTn….….144
Figure 19. Annual Trophic energy flow among planktons at HBM and SBM……………146
Figure 20a. Trasfer of trophic enegy at LT and HT during a complete tidal cycle………..147
Figure 20b. Trasfer of trophic enegy at MT and LTn during a complete tidal cycle………148
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ABSTRACT From Northern Arabian Sea bordering Pakistan this is the pioneer study on the diversity, density and effects of mangrove energy flux on zooplankton community structure. The study focusses on three aspects; Mesozooplankton (MZ) abundance, Copepod diversity and effect of mangrove energy flux on MZ. The study was conducted at four stations (OC, HS, SBM and HBM) covering the inshore waters of Manora channel. Annual and seasonal variations in density of 21 zooplankton group was estimated with respect to change in habitat with different environmental influences. Density of these groups were high at 5m depth. The Copepods were the most abundant meso-zooplankton group at all stations except at OC followed by cladoceran, gelatinous zooplankton, nematodes and polychaete larvae respectively. Cladoceran was high in density (127700 Ind-m-3) at OC. Salinity, temperature, dissolved oxygen and Chl a concentration was found to effect the distribution of MZ. Cladoceran showed strong relation with salinity and Chl a at OC and HBM. Temperature variation effect the distribution of gelatinous zooplankton strong (F=10.22; P=0.008). Highest density of nematode (12133 Ind-m-3) and polychaete larvae (35600 Ind-m-3) were recorded at HBM and HS respectively. Mangrove stations were highly diversified as compare to other two stations. Even though the high abundance was recorded from OC but highest diversity was attributed to the mangrove stations.
High abundance and diversity of zooplankton was found during SWM monsoon season. MDS ordination reveals the 80% similarity between SWM and NEM seasons. Highest values of Chl a were obtained in December at mangrove stations HBM and SBM (59µg-L-1 and 72 µg-L-1 respectively). Classical relation of primary producers and zooplankton was recorded at all stations. From September to November the low concentration of phytoplankton biomass was recorded and at the same time the high zooplankton density was noted. Similarity was noted between SBM and HS as SBM receives hydrological influence from HS whereas, OC receives influence from HBM.
A total of 69 species of copepods was recorded during this study. 47 species were identified under the order Calanoida, 17 species in order Cyclopoida and 3 species of harpacticoid copepods were identified. Out of 69 species, 23 species has been observed for the first time from Pakistani waters. The family Temoridae, Paracalanidae and Pseudodiaptomidae were the dominant among Calanoid. Within the cyclopoid copepods Corycaeidae, Oithonidae families were dominant throughout this study and 6 species of genus Oithona were recorded xi
first time from Pakistan during this study. Euterpinidae family was the most dominant harpacticoid family with the single genus Euterpina acutifrons. Variations in diversity and density was noted between stations. Eucalanus bungii, Eucheata marina and Pontella securifer was totally absent from station HS. Candacia discaudata, Acartia ohatsukai and Copilia vitrea was totally absent at OC. Rhincalanus Sp., Clausocalanus minor, C. karachiensis, C. chierchiae, C. alocki, Candacia sp., Pontella securifer and Calanopia sp. were not recorded at HBM.
Effects of mangrove energy flux on zooplankton community was accessed by the phytoplankton production and its trophic partaking to primary consumers which are zooplanktons. Major nutrients concentrations were determined to study the effects of nutrients on primary production. HS, a polluted station, was rich in NH4 and NO3 concentrations as compared to OC. At HBM substantial relation of NH4 was recorded with the phytoplankton biomass. Although nutrients provide energy for the growth of phytoplankton, other physical variables are also responsible for their growth such as temperature, DO and turbidity. Annual findings illustrate that the omnivore zooplankton were the major consumers in mangrove forest among the functional feeding groups of zooplankton. 56% and 59 % space was occupied by the Omnivore group at HBM and SBM respectively. Only 2-4% of the total zooplankton were detritivores.
The tidal cycle was covered at HBM to study the mangrove influence. Overall nutrient concentration was high at MT and low at HT indicating outward flux of nutrients from mangroves. The same pattern was noted for phytoplankton biomass. Zooplankton density was high at HT and LTn as during night the zooplankton moves towards the surface. The phenomena of Dial-Vertical Migration was noted during tidal cycle as indicated through the high density of zooplankton during night sampling. The omnivore zooplankton were high during HT and MT. Inverted energy pyramids was formed at LTs where the detritivore zooplankton dominated the other groups. The out-welling of detritus from mangroves might be the possible cause of high abundance of detritivores at LTs. The results reveals that the study area supports high diversity and density of zooplankton. The variations in species composition between stations indicates the effect of environmental influences. The energy flux from mangroves appears to support the high diversity of zooplanktons not only within mangroves but to the surrounding waters outside the Manora Channel.
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INTRODUCTION TO CHAPTER # 1
THE DISSERTATION
INTRODUCTION
Ocean is 71% of the earth. Which is the largest ecosystem on the earth. Planktonic creatures exhibit top layer of the ocean which is the euphotic zone. This euphotic layer is top 200m where the production activities exhibit (Lalli and Parsons, 1993). Phytoplankton and zooplanktons are the basis of marine ecosystem. After 1980s the concept of microbial food web became clear, which describes the flow of energy due to microbial activities. Marine bacteria play vital role in the microbial food chain through mobilization of organic carbon (Azam et al., 1983).
Phytoplankton constitute the first link in the marine food web as primary producers, consumed by many organisms, including zooplanktons and other consumer organisms (for example, baleen Whales) at higher trophic level. The growth of phytoplankton is dependent on various biotic variables, preferably nutrient concentrations, intensity of light and temperature (Eppley, 1972). Phytoplankton communities are composed of multi-species assemblages specially diatoms which depends on abiotic parameters to regulate their diversity and abundance (Mendes et al., 2009). Chlorophyll a is the measure of primary productivity and their production depends on the adequate supply of water nutrients and other abiotic factors (Cloem et al., 2014; Zhou et al., 2004; MacIntyre and Cullen, 1996).
Zooplankton include all floating animals and are found in abundance in waters where abundant food is present. Zooplanktons are minute creatures that feed on other planktons. They migrate vertically and horizontally according to the intensity of the Sun light. During the day time they migrate down and at the night time they come near to the surface. Some zooplanktons are actually larvae that eventually change into worms, molluscs, crustaceans etc. are known as Meroplankton. Some zooplanktons spend their entire life cycle as plankton e.g., pteropods, chaetognaths and copepods. Copepods, the main group of zooplankton graze upon the phytoplankton within the mangrove ecosystem (Dahms and Qian, 2005; Feng et al., 2018). Small zooplankton faces less predation by planktivore fish while they were mostly predate by the large sized zooplankton (Gliwicz and Pijanowska, 1989; Brierley et al., 2017). Zooplankton
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abundance is reported to be strongly influenced by certain environmental variables (Hunt, 2014; Beaugrand et al., 2000).
Marine ecosystems sustained by the mangrove forests which keep the shoreline in steady state and provide shield to inshore areas (Odum and Heald, 1975). Halophytic zooplankton play vital role in the chemical cycle in mangrove areas, they also endow food to the other consumers of mangrove habitat and marine ecosystem (Mitch and Gosselink, 1993). Nutrient energy flux in mangrove ecosystem mainly depends on Nitrogen and Phosphorous fluxes (Valiela and Teal, 1979; Davis, 1994; Feller, 1995). The surplus nutrients in estuarine may cause eutrophication which cause dense growth of algae, and consequently reduces the dissolved oxygen, transparency of water and disturbed the floral and faunal habitat. Thus, mangrove ecosystem were reported to influence the nutrient cycling (Hobbie, 1992) and play vital role as a nursery area for zoobiota (Chong et al. 1990, Louis et al., 1995, Barletta-Bergan et al. 2002). They provide food to fish juveniles and diminish the chance of predation (Laegdsgaard and Johnson 2001). The grazing of zooplankton is reported to increase the particle flux in vertical column of a water body (Harris et al., 2000). As a result of predation the zooplankton integrate prey into biomass and liberate the nutrients in water column thus play important role in supply and descend of the nutrients (Wavle and Larsson, 1999).
Zooplankton are the indicator of fishery potential of the area and hence information on its interaction with other micro planktonic groups is important in fishery management. Numerous studies in past shows the influence on planktonic communities by different physical processes (Huskin et al., 2001). Environmental factors such as, temperature, salinity and nutrients, are reported to be the main factors controlling phytoplankton production (Eppley, 1972). Shore erosion by tidal flow during cold and spring seasons support the nutrients production and growth of planktons, whereas, the high temperature help in the regeneration of essential nutrients (Rho et al., 2005).
Monsoonal effects on the distribution of zooplankton community has been briefly described from NW Indian Ocean (Smith et al., 1998). From the other parts of Indian Ocean the seasonal driven changes was recorded during monsoon (Cushing, 1973).
3
The distribution and taxonomy of the copepods occurring in the western Indian Ocean (WIO) received attention worldwide. First report on the distribution of pelagic copepods was published by Giesbrecht (1889). Ahmed et al., 1993 describes that the
Figure 1. World Ocean data base 2009, geographical distribution of (a) phytoplankton (37,461 casts). (b) Zooplankton (44,303 casts). White Point representing the northern Arabian Sea clutches of planktons. (Baranova et al 2009).
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Fauna of this region is unique as compare to the other Oceans. Some of the important works on copepods distribution and taxonomy in the WIO include Pillai, 1978; De Decker and Mombeck, 1965; Grice and Hulsemann 1967; Kasturirangan. et al., (1973), Fleminger and Hulsemann, 1973; Lawson, 1977; Rajaram and Krishnaswamy, 1980; Stephen et al., 1992; Gajbhiye et al., 1991; Gopalakirshnan and Balachandran, 1992; Niop, 1992, Arabesque, 1994; Goswami, 1994; Al-Yamani et al., 1995, and Razouls (1993, 1995, 1996, 1998, 2005).
With regards to Pakistan, literature on distribution and abundance of planktonic communities is scarce and most studies conducted in the past deals only with taxonomy. The history of the copepod taxonomic investigations in Pakistani waters dates back to Bindra (1924). The reports on zooplankton of Karachi coast published by the Ahmed (1951), Ali and Arshad (1966). Haq (1968) published a paper on the variations of Undinula vulgaris in northern Arabian Sea. Gololobov and Grobov (1970) worked on the biomass, distribution and quantitative zooplankton composition in the Arabian Sea. Fazal-ur-Rehman, 1973, contributed two new species: Pontella karachiensis and Centropages karachiensis from the coastal waters of Pakistan. The data on the abundance of zooplanktons from the coast of Pakistan were reported by Haq and Fazal-ur-Rehman, 1973; Khan and Khan, 1978; Meher, 1983; Khan, 1995. Abundance of Fish larvae were studied in the samples collected during NASEER cruises (Kidwai and Amjad, 2001).
The research on zooplankton diversity and abundance receives little attention and the information on the annual and seasonal distribution of zooplankton, interaction of zooplankton to the phytoplankton biomass and species diversity in the inshore waters and mangrove forests of Pakistan is not available. This study was designed to fill the knowledge gap about the zooplankton species diversity, abundance and the effect of energy flux on the distribution of zooplankton. The present study was the first through study on zooplanktons from Pakistan.
5
AIMS AND OBJECTIVE OF STUDY
The study was conducted in 2012 to 2013 at two stations in mangrove forests and in addition one at polluted area and one in coastal waters to assess the:
1. Physico- chemical parameters and their effects on the distribution of zooplankton.
2. Assessment of variation in phytoplankton and zooplankton biomass.
3. Qualitative and quantitative assessment of seasonal variation in zooplankton abundance.
4. Copepod species composition and abundance.
5. Similarity between studied stations.
6. The effect of mangrove energy flux (through nutrient and phytoplankton biomass) on zooplankton diversity and abundance.
7. The influence of tides and day-night cycles on the zooplankton.
STRUCTURE OF THESIS
This dissertation is split into 4 chapters. Chapters are the consequences of research conducted throughout the sampling years. Chapter 2 to 4 are the main outcome of the study.
Chapter 1 is about the general introduction of the study, theme of the study. Aims and objective of research given in this chapter.
Chapter 2 defines the mesozooplankton community (MZ) with reference to hydrological parameters. The MZ are the indicators of healthy fisheries. The seasonal and vertical variations in density of 21 MZ groups and their relationship with phytoplankton biomass (Chl a) was described. Variations between stations is also given in this part of dissertation.
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Chapter 3 is about the species diversity of four taxonomic orders of copepods: Calanoida with 47 species, Cyclopoida with 17 species, Herpacticoida with 3 species and a single representative of the order Monstrilloida. 68 of the total copepods were identified and their ecological abundance were estimated at four stations in mangrove and outside the mangrove areas. Seasonal copepods abundance was estimated during monsoon seasons at all stations.
Chapter 4 illuminate the effect of energy flux in terms of the nutrient analysis at mangrove stations HBM and SBM. Although the estimation of nutrient was recorded also from non mangroves stations but the emphasis given to mangroves stations. Within the mangrove ecosystem these nutrients make fluxes on behalf of mangrove litter production. This energy transfer to the phytoplankton community for their multiplication which were directly consumed by the primary consumers. To some extent the effect of this energy flux was determined on the distribution of zooplankton community in mangrove forests. In addition with this the consequences of the tidal cycle at station HBM was represented in this chapter.
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CHAPTER #2
ENVIRONMENTAL EFFECTS ON ZOOPLANKTON COMMUNITY DYNAMICS AND ABUNDANCE IN COASTAL WATERS, MANORA, PAKISTAN
Mubeen Ara 8
ABSTRACT
Mesozooplankton (MZ) community structure was estimated at two mangrove (HBM and SBM) and two non-mangrove (HS and OC) stations with the influence of physical and biological parameters. The temperature was ranged from 19.6 oC to 33.7 oC, salinity was ranged between 20-46 ppt, and dissolved oxygen between 1.15-13.6 mg / L at all stations. Chl a ranged from 0.01-74 µg/L. A total of 21 MZ groups and 1604136 individuals of mesozooplankton (MZ) was counted from all stations during this study. Cladocera was the most dominant group which constituted 70% of MZ during October. As compare to other three stations OC waters was dominated by cladocerans with the total annual density 127700 Ind.m-3. The comparison of total MZ and total copepods groups indicate higher copepod abundance except at OC where high MZ (190666 Ind.m-3) and low copepod abundance (164933.3 Ind.m-3) was recorded during October. Classical relationship between phytoplankton and zooplanktons was also observed. Shannon diversity was high during SWM and POM. Among stations the high diversity was found at HBM in SWMS ( d = 3.971; H = 2.92). Cladocera and nematodes showed significant relation with salinity and gelatinious zooplankton showed significant relation with temperature. MDS showed 80% resemblence between mangrove stations HBM and SBM with respect to MZ seasonal abundance.
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1. INTRODUCTION
Planktons are the organism which rely on the drifting power of water for movement (Kennish, 1990).They vary in size which ranged from 2µ to 2 cm (Levinton, 1995). Planktons have been group and into phytoplankton and zooplankton, some of them exhibit as a plankton for a short time in their lives (meroplanktons), such as eggs, fish larvae, and early life stages of shrimps, crabs, and molluscan and echinoderm larvae. Mesozooplankton (0.1 - 2.0 mm) are microscopic animals which includes the diverse group of small planktonic taxa. Their cosmopolitan occurrence play vital role in the ecosystem where they are the key factor in food web, nutrient regeneration and its transfer from primary producer (phytoplankton) to primary consumer (zooplanktons) and then to secondary consumer such as fish (Banse, 1995; Cook et al., 2007; Andrew, 2001). Economically these planktons (zooplanktons) regulates the fisheries worth globally (Evjemo et al., 2003). In classical food chain the dominance of fish production was related with the high population of planktons. Along the chief link of zooplankton with fisheries, the importance of these tiny world cannot be neglected in the perspective of oceanography. In Oceans they perform the role in settling of organic particles from up to down the phenomena is known as biological pumping (Boyd and Newton 1999). The utilization of phytoplankton by copepods also result in the high organic production (Smetacek, 1985; Wassmann, 1991). By analysing zooplankton biomass and abundance the stress on the ecosystem by different physical, chemical and biological parameters can be analysed because of their sensibility to response any change in environment (Magadza, 1994; De´sire´e et al., 2013). In mangroves they also exhibit important role in transferring energy from producers to high trophic levels. (Mclusky and Elliot 2004; Bedford et al., 2018; Belgrano et al., 2005). Mesoscale variation occurs in spatiotemporal distribution of zooplankton within coastal and inshore waters (Powell, 1995; Ashjian et al., 2001). The variation in species composition of zooplanktons is improbably inclined by invertebrate predation (Hall et al., 1976). Zooplankton community in estuarine areas were controlled by tidal force as well as the fresh water flow which drive the riverine and marine community together in estuarine ecosystem (Waniek et al., 2005). Hydro- biological, physical and chemical variables have reported to influence the structure of
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plankton community in marine ecosystem (UNESCO 1981; Bianchi et al., 2003; Hsiao et al., 2004; Hays et al., 2005; Sridhar et al., 2006; Feudel, 2018). Besides their critical presence in food web their occurrence and population dynamics in coastal and mangrove area, is determined by the biological, chemical and physical processes. The effects of physical parameter such as temperature (Austin and Jones, 1974), and salinity (Silva et al., 2009; Zervoudaki, 2009) on zooplankton distribution has been noticeably studied. The spatial and temporal distribution of zooplankton species (Kelly and Dragovich, 1967; Badylak and Phlips, 2008) as well as their trophic status has been identified (Leising et al., 2005). Environmental situations in estuarine areas fluctuate rapidly which powerfully affect the distribution of mesozooplankton (Dauvin et al., 1998). Most of the zooplanktons species tolerate wide range of fluctuation in ecological parameters, while certain species were influenced by abiotic factors such as salinity, temperature and dissolved oxygen (DO) and biotic interaction. Among all abiotic factors the salinity plays vibrant role in the osmoregulation of the marine zooplankton species and effects heir distribution and abundance (Ojaveer et al., 2010). Zooplankton community construction is mainly based on the presence and distribution of species in ecosystem (Fulton, 1984). Not all species reveals the same impact of physical parameters on their occurrence. Each species or groups have changing ability or intensity of tolerance to environmental change (Tunowski, 2009). Among mesozooplankton cladocerans and appendicularian has been reported for their instant response to the change in environmental parameters whether in their favour or against to them (Lipej et al., 1997). Diversity and population of zooplankton directly relate with the fish production (Mishra and Panigrahy, 1996). The zooplankton utilize mangrove forest as either permanent or transitional habitat and act as important link in energy transfer in mangrove ecosystem (Robertson and Blaber, 1992). Little research has been published regarding zooplankton of mangrove habitats worldwide. Copepods, which are the most abundant mesozooplankton, were reported to have high abundance in mangrove forests as compare to coastal waters (Robertson et al., 1988). The high abundance of copepods (MZ) may be linked to the high chlorophyll content in the area (Soreide et al., 2010). The lower predation also increased the survival rate for zooplankton in mangroves (McFarland et al., 1985; Cocheret et al., 2004).
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Previously cited literature on mesozooplanktons from Pakistani waters contributed by Muhammed and Arshad (1966), Haq et al., (1973), Ali-Khan and Hempel (1974), Ali- Khan and Ali-Khan (1978), Huda and Ahmed (1988), Tirmizi and Nayeem (1992), Huda (1993) Rizvi et al., (1994), Amjad et al., (1995). The knowledge about the mangrove MZ community is very limited and poorly evaluated in the past. Monsoonal abundance of zooplanktons has been investigated in 1975-1977 in Manora Channel (Khan, 1979). The current study was also conducted at two mangrove and two non- mangrove stations in Manora channel to assess the community structure and abundance of different MZ groups like coelenterates larvae, nematodes, polychaete larvae, gastropods, lucifers, cladocerns, ostracodes and gelatinous mesozooplanktons which includes ctenophores, medusa, appendicularia and slaps. The influence of different chemical biological factors on MZ was also evaluated.
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2. MATERIAL AND METHODS
2.1. COLLECTION SITES
Northern Arabian Sea is bodering Pakistan. Karachi is the biggest city of Pakistan lies on the northern Arabian Sea with the coastline of 70km Manora is the main island in Karachi which is serving as trading channel. The study area was Manora channel. This channel is the main trading navigational channel. Tidal pattern is semi-diurnal in this area (Quraishee, 1975). Four stations were selected in semi enclosed inshore waters. This area is enclosed with three different habitats which includes mangrove forests, layaari river outlet and mouth of the channel from where channel is linked with the open ocean. Out of the selected four stations two stations were established in mangrove forest and one station was selected near Karachi harbour and the fourth station was located just outside the Manora channel mouth. The stations were selected to study the abundance and effect of energy flux on zooplankton by inflow of Open Ocean into the channel and out flow of inshore waters towards Open Ocean.
2.1.1. Non-mangrove stations OC and HS
Two stations were selected outside the mangrove forest to estimate the effect of the different water bodies on MZ (Figure 1). Open Ocean (OC) 24046’05.91”N, 66059’44.32”E station is located off the mouth of manora channel, OC recives directly the effects of waves actions and tidal fluctuation from open ocean.
Harbour station (HS) 24050’41.39”N, 66058’09.72”E, is located near the Karachi Fish harbour. This station is a polluted site because of the Layari River outlet. The Layari River discharge domestic and industrial effluents at this site ( Beg et al., 1984). Due to natural geographical situation of Karachi harbour, marine pollutants are not completely flushed out into the open sea (Ahmed, 1979; Beg et al., 1984).
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2.1.2. Mangrove forest station HBM and SBM
Two stations were located in mangrove areas to study the influence of mangrove on the zooplankton. Sandspit back water mangroves (SBM) lies at 24050’40.96”N, 66056’34.85”E and Himalaya backwater mangroves (HBM) at 24049’15.85”N, 66057’24.40”E (Figure. 2). The station HBM is located near Baba and Bhit island. The stations receives influence from the open ocean through ChariKund Channel. Tidal water from Manora Channel enters in mangrove forests at station HBM and SBM twice in 24 hours. Tidal fluctuations move sea water from open Ocean in and out at both SBM and HBM through Manora channel.
Figure 1. Study site map showing collection sites in side Manora channel and outside Manora channel.
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Figure 2. Sampling sites. HS (Harbor station), OC (Open Ocean) and mangrove forest stations HBM (Himalaya backwater mangrove) and SBM (Sandspit backwater mangrove).
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2.2. SAMPLING AND ANALYSIS
2.2.1. COLLECTION AND ANALYSIS OF PHYSICOCHEMICAL PARAMETERS
Sampling was done monthly at high tide preferably at early morning from Sept 2012 to Sept 2013 at all four selected stations SBM, HBM, HS and OC to evaluate the annual and seasonal variations in abiotic and biotic factors during pre south-west monsoon (PRE), South-west monsoon seasons (SWM), post monsoon season (POM) and North-east monsoon season (NEM). Sea water was collected from surface for the analysis physicochemical parameters. Surface water temperature, Salinity, pH, and water transparency were estimated on site. Temperature were noted with the help of digital thermometer (Hanna, Inc.), Salinity by refrectometer (Atago, Japan) and pH by pH meter (Hanna, Inc.). Sample for DO were collected in dark amber glass bottles and fixed without delay on site and later determined by Azide-winkler titration method. 60 ml of sea water sample was fixed on site in BOD glass bottles, 1ml of manganese sulphate (MnSO4) and 1 ml of alkai-iodide-azide (KI) were used for fixation. Precipitates were formed which were dissolved by using 1 ml of sulphuric acid to the BOD bottles. The fix samples were later titrated with the sodium thiosulphate.
Transparency of the study zone was estimated by lowering cleaned secchi disk. For TSS analysis water samples were stored in pre-cleaned plastic bottles at -20 0C. The sample for the analysis of total suspended solids (TSS) were filtered out with the help of the filtration assembly by following the standard method (APHA, 1997). For filtration pre weighed GF/F filters were used. The amount of TSS was calculated by:
Total suspended solids (TSS) = A*1000 / Volume of filtered water Where, A = calculated residue after oven dry
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2.2.2. COLLECTION AND ANALYSIS BIOLOGICAL PARAMETERS
Estimation of Phytoplankton Biomass
The phytoplankton biomass was estimated through chlorophyll analysis. The samples were filtered in duplicate on the same day of collection through glass fibre filter papers by using filtration assembly. After filtration the filter papers along with residue were transferred to 90 % acetone and were set aside in dark at 4 OC for at least 24 hours. Chlorophyll a and Phaeopigments was determined spectrophotometrically by following the method as described by Strickland and Parson, 1972, and the pigment content in the samples were determined by using the formula:
Chlorophyll mg /L = C X ѵ / V X 10
Where,
C= Respective calculated chlorophyll a, b and c
ѵ=Volume of extract
V= Volume of sea water.
2.2.3. ZOOPLANKTON COLLECTION AND ANALYSIS
Zooplanktons were collected through zooplankton net with the mouth diameter 0.29m and 170 micron mesh size. Two vertical samples were taken from each station from surface (0.5m) and from 5m depth. Zooplankton sample were transferred from net to the cleaned wide mouth plastic jars. Immediately on boat samples were preserved in 4% buffered formalin and the samples were kept in dark. Abundance of identified groups was estimated by counting zooplanktons in counting chamber under binocular stereomicroscope. Standard methods for zooplanktons laboratory handling were used as described in ICES techniques (Harries et al., 2000). Different groups were identified by the help of previously cited literature and keys (Newell and Newell, 1973; Al- Yamani et al., 2011).
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2.2.4. ZOOPLANKTON DENSITY
By following the ICES manual the preservation and labortary handling was performed. For the estimation of zooplankton abundance and density the standard method was followed. Volume of water filtered from net was used to determine the zooplankton density which was calculated by using the area of net and data was standardised to Ind.m-3.
2.3. STATISTICAL ANALYSIS
Cluster analysis on data was performed, based on Bray-Curtis similarity matrix to visualize the corelation between MZ and stations by using PRIMER 6.1 (Clarke, 1993; Clarke and Gorley, 2006). MDS was performed to analyse the seasonal resemblance of stations. Dendrogram was made via Bray-Curtis similarity matrix to evaluate the similarity among MZ at four stations. Diversity indices (Shannon wainer diversity indices) was performed to visualise the diversity among stations during monsoonal seasons. Regression analysis and ANOVA was performed between the groups and physicochemical parameters.
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3. RESULTS
3.1. VARIATIONS IN ENVIRONMENTAL PARAMETERS
Environmental parameters were observed throughout the sampling period from all four studied stations. Significant variation were observed between stations. The mean temperature were recorded from 19.6 – 33.7 oC (Table 1). The lowest Temperature (19.6 oC) were recorded in December and the highest in June (Figure 3).
Salinity fluctuations at stations were shown in Figure 3. Annual variation in salinity was observed between stations from 20 ppt to 46 ppt. Mangrove site HBM reflected slightly higher salinity as compare to SBM (Figure 3). The lowest salinity were recorded at SBM and HS during October 12 (20 ppt). Highest average salinity was recorded at OC (39.6 ± 5.15). HS and SBM show similar pattern of salinity distribution throughout the year. From December to February the high salinity was recorded from all four sites. Highest value were traced out at HS during December (46 ppt) (Figure 3). The variation in transparency of sea waters at stations was given in Table 1. . The high clarity in water was recorded at OC.
The pH values were ranged from 7.4 - 8.14 throughout the study period at all stations (Table 1). The highest value of pH were recorded from coastal waters, OC (7.88) in the month of May (Figure 4). No significant change in pH was observed between stations. Monthly pH change at four studied stations was given in Figure 4.
Variation between transparency and TSS was illustrated in Figure 5. TSS values at HS and OC were high (0.26 - 0.21 mg L-1) as compare to the mangrove sites HBM and SBM (0.09 - 0.097 mg L-1) (Table. 1). Higher TSS makes water turbid thus decreasing the transparency. The high transparency were recorded at OC as compare to mangrove stations HBM and SBM.
The annual fluctuation in DO concentration is given (Figure 4). DO concentration varied from 1.15 to 13.6 mg L-1. The high DO concentration was recorded from HBM (13.6 mg L-1) respectively. Throughout the study period the highest value were
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observed during April from HBM. Lowest values were recorded during May and June (1.15 mgL-1) at HS.
Chlorophyll a concentration showed significant variation within a year (Figure 6). Lowest concentration was observed from September to November, April and July at all four stations. High concentration was obtained in December (59.6 µg/L) at HBM and in May (74.9 µg/L) at SBM. Among mangrove stations HBM and SBM, the highest concentration was obtained from SBM which was 74.9 µg/L and the lowest (0.01 µg/L) was recorded from HBM (Figure 6). The concentration of Chl a was ranged between 0.003-55.9 µg/L at non-mangrove stations HS and OC (Table 1).
Table 1. Physical and biological parameters ranges and annual mean values from mangrove and coastal stations.
Mangrove Zone Non-Mangrove zone Parameters HBM SBM Range HS Range OC Range Mean±SD Mean±SD Min-Max Mean±SD Min-Max Mean±SD Min-Max T oC 27.1±3.19 26.9±3.3 19.6-33.6 27.2±3.1 21-33.7 27.03±2.88 20.5-31.6 Salinity (ppt) 39.56±4.7 38.19±6.9 20-45 36.76±7.1 20-46 39.69±5.15 30-45 pH 7.6±0.141 7.68±0.17 7.4-7.98 7.67±0.2 7.4-8.05 7.88±0.16 7.54-8.14 (DO)mg/L 9.60±8.9 6.31±3.33 2.01-13.6 7.49±5.6 1.15-11.3 10.17±6.12 1.53-13.3 Transperancy(m) 0.79±0.49 0.9±0.67 0.3-2.5 1.13±0.6 0.2-2 1.9±1.00 0.3-4 TSS ( mg/L) 0.09±0.09 0.097±0.09 0.001-0.25 0.26±0.42 0.00325-1.2 0.21±0.48 0.0005-0.24 Chl a (µg/ L) 21.3±21.7 24.9±27.2 0.01-74 18.3±2.06 0.003-55.9 16.00±22.3 0.003-55.9
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Figure 3. Annual fluctuation of physicochemical parameters (Temperature and Salinity) at all studied sites, HS and OC and two Mangrove sites HBM and SBM.
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Figure 4. Annual variation in pH and dissolved oxygen (DO, mg-L-1) at HS, OC, HBM and SBM.
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Figure 5. Annual variation between transparency (m) and TSS (mg-L-1) at HS, OC and mangrove sites HBM and SBM.
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Figure 6. Comparison of Annual variation in phytoplankton biomass (Chl a) between HS and OC and mangrove forests, HBM and SBM.
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3.2. MESOZOOPLANKTON DIVERSITY AND
ABUNDANCE
A total of 21 groups of MZ were recorded in the present study. Figure 17 shows the comparison of diversity indices between stations. Marked variations were observed between seasons at stations. The diverity indices were high during SWM except OC where comparatively high diversity has recorded in NEM and lowest during POM (Figure 7). Among stations the species richness and Shannon-Weiver diversity index was high at HBM ( d = 3.971; Hˈ = 2.92).
The monthly relative abundance of other groups of MZ excluding copepods during studied period shown in Table 2. Throughout the study periods the MZ expressed their high abundance in 5m depth as compare to the surface waters. This pattern of vertical distribution showed the movement of MZ in water column. High relative abundance of MZ was recorded in October and less in June 2013 Relative abundance of coelenterate, ctenophores, planktonic worms, and lucifers were very low as compare to the other MZ groups. Echinoderms were not found in surface water samples except in September 2013, they were only recorded in 5m waters in less numbers (Table 2). Polychaete larvae were high during September 2012, 2013, November and February. Nematodes, polychaete larvae and nauplii were found in high numbers during April, May, July and September 2013 which are the spring monsoon (PRE) and southwest monsoon (SWM) months respectively. During June only planktonic worms, Doliolids and Nematod were recorded. Overall, the cladocerans was the most abundant MZ followed by polychaete larvae, appendicularians and chaetognaths.
The comparison of total MZ between stations was given in Table 3. Higher abundance of majority of MZ groups were recorded from OC. Polychaete larvae, other planktonic worms, ostracods, echinoderms and appendicularians showed high abundance at HS. Highest density of nematods (12133 Ind.m-3) was recorded from HBM followed by HS (5500 Ind.m-3). Ctenophores and salps were comparatively high in abundance at SBM.
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Cladocerans showed high percentage of occurrence at all stations (Table 3). The other planktonic worm showed lowest abundance at OC (0.00026 %) and highest at HS (0.710 %). The comparison of mean abundance between stations indicate high abundance of majority of MZ at non-mangrove stations HS and OC. Ctenophore, nematodes, ostracods, chaetognaths and salps were found to be more abundant at mangrove stations HBM and SBM (Table 3).
Table 4 showed the mean vertical abundance of copepods during study period. The high abundance of copepods were also recorded from non-mangrove stations HS and OC. As compare to mangrove stations. In March, May and June copepods were high in abundance at mangrove stations. The high density of copepods were recorded in October May, December, March, August and September. The low abundance were recorded during April and June. Throughout the study period the highest mean abundance of copepods were recorded at HS during October (Total abundance = 79466 Ind. m-3) followed by mangrove station SBM (Total abundance = 64733.33 Ind.m-3 in May). Comparatively higher abundance of copepods was recorded from 5m depth.
The variation among MZ from September 2012 to September 2013 were shown in Figure 8-14. Habitat driven changes were recorded during monthly abundance estimation. In the month of September 12, the polycheate larvae were high in abundance (4066.667 Ind.m-3) in the surface waters of HS and OC. The comparative abundance of cladocerans where high in 5m waters (Figure 8). From October to January cladocerans showed high abundance at OC (7833.33 Ind. m-3 ± 152 at 5m in November), with no difference in vertical distribution, except for surface waters of November where density of polycheate larvae were comparatively high. (Figure 8-9). In February the polychaete larvae were high in density in both surface and deeper waters at OC and HS respectively. In Mangrove stations and lower abundance of MZ were recorded as compare to OC (Figure 10). Cladocerans show high abundance at OC and HS respectively during March and April (Figure 11). During May the nematode was high in numbers at HS and nauplii showed high abundance in surface water at both SBM and HBM. In the month of June only nematodes and doliolids were recorded and rest of the MZ were absent in the samples collected from all four
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stations. Nematods were high in density with very less number of doliolids (Figure 12). In the month of July the count of nauplii was higher in the surface waters at OC as compare to 5m (Figure 13). In August the highest density of cladocerans and ostracods were recorded at OC (Figure 13). The appendicularians were high in abundance at HS and SBM (Figure 13). In September 2013 the zoea were high in abundance at HS both in surface and 5m (Figure 14). The polychaete count was low in September 2013 as compare to September 2012. Cladocerans, nauplii, Zoea, Polycheate larvae, and appendicularians were the most abundant taxa during the studied period.
15 Figure shows the comparison of MZ with copepods. Copepods was the most dominant group among MZ at all stations except station OC where copepods were comparatively less abundant (15 %) as compare to the other MZ at all stations (Figure 15).
During the study period the highest mean density of MZ and copepods were recorded during October (190666 Ind. m-3 and 164933 Ind. m-3 respectively). While the lowest density of MZ (400 Ind. m-3) and copepods (1049 Ind. m-3) were obtained during June (Figure 16). Overall the mean annual MZ were higher in abundance at OC and HS in contrast to HBM and SBM (Figure 17).
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Table 2. Relative abundance (%) of different studied groups of MZ (excluding Copepods) in surface and 5m waters (in parenthesis). *Marine planktonic worms include all identified worms.
Groups Sep.12 Oct. 12 Nov. 12 Dec. 12 Jan. 13 Feb. 13 Mar. 13 Apr. 13 May. 13 Jun. 13 Jul. 13 Aug. 13 Sep. 13 Coelentrate 0.84 (0.27) 0.22 (0.03) 4.66 (1.80) 2.45 (0.97) 1.67 (0.36) 0.92 (0.82) 0.41 (2.061) 0 (0.21) 0.59 (2.01) 0 2.32 (6.96) 16.7 (17.71) 5.48 (5.09) Ctenophores 0.89 (0.12) 0 0 (0.13) 0 (0.62) 0 0 0 0 0 0 0 0.15 (0.19) 0.29 (0) Nematods 0 3.45 (1.27) 2.91 (3.22) 10.73 (10.61) 0 (0.54) 1.11 (0) 0 4.81 (1.00) 31.95 (19.06) 42.55 (93.61)20.34 (3.47) 0 0 (1.56) Polychaete larvae 22.8 (8.42) 6.75 (2.56) 37.00 (21.39) 9.60 (8.89) 10.63 (3.95) 35.60 (22.45) 3.42 (3.64) 4.81 (10.02) 2.37 (10.03) 0 4.06 (7.83) 1.03 (0.66) 25.04 (18) Marine planktonic worms 6.07 (3.65) 0.27 (0.05) 0 (0.008) 0 0 0 0 0 1.18 (0) 0 (2.12) 0 0 0 Gastropods 1.34 (1.06) 0.49 (1.04) 6.24 (6.44) 1.13 (2.49) 0.61 (0) 1.66 (0) 3.01 (3.51) 0 (2.004) 0 (3.01) 0 0 (1.739) 1.03 (1.31) 3.11 (1.17) Bivalves 1.84 (1.690) 1.32 (0.68) 0 (2.83) 0 (2.01) 1.37 (0) 0 (0.41) 0 (0.89) 6.73 (5.41) 0 (5.02) 0 0 1.61 (0.37) 0.89 (1.07) Nauplii 13.4 (22.42) 5.66 (4.76) 0.83 (3.86) 15.81 (23.31) 9.57 (18.70 14.02 (18.13) 10.38 (10.37) 28.84 (32.86) 35 (17.4) 0 31.98 (31.30) 20.09 (16.5) 12.15 (11.44) Zoea 7.02 (8.02) 4.87 (4.39) 0 (6.18) 1.69 (9.51) 11.09 (6.5) 6.08 (4.02) 9.56 (8.32) 2.88 (0.60) 2.37 (7.69) 0 19.77 (32.17) 7.77 (10.40) 27.7 (26.5) Mysids 0 (0.96) 0.73 (0.79) 0 0 (0.14) 2.43 (0.35) 0 (0.21) 0 (0.96) 0 1.18 (0.67) 0 2.91 (6.08) 0 1.92 (1.07) Lucifers 1.00 (2.29) 1.02 (0.39) 0 (0.39) 0 0 (0.72) 0 (0.20) 0 (0.21) 3.84 (6.01) 0 0 0 0 (0.37) 0 (0.49) Cladoceran 30.41 (38.09) 70.12 (80.06) 30.77 (33.11) 51.60 (34.28) 39.66 (54.49) 23.61 (28.83) 50.40 (47.15) 31.73 (26.65) 4.14 (9.36) 0 0 22.72 (24.6) 2.66 (12.03) Ostracods 0.83 (1.38) 0.30 (0.42) 1.25 (0) 0.37 (0.83) 0.61 (0.89) 0 (0.20) 0.68 (2.27) 0 5.91 (6.35) 0 0 (3.48) 7.18 (10.5) 0.59 (0.19) echinoderm 0 0 0 0 (0.69) 0 0 (1.85) 0 0 (0.80) 0 0 0 0 0.89 (0.8) Chaetognatha 1.39 (2.74) 1.14 (0.46) 1.66 (3.99) 4.71 (3.26) 7.29 (1.79) 0.92 (2.26) 11.07 (6.12) 0 3.55 (7.69) 0 8.72 (0) 0.15 (0) 0 (0.29) Salpas 0.39 (0.66) 0 (0.09) 1.25 (0.26) 0.18 (0.28) 1.22 (2.52) 0.55 (0.51) 0.14 (0.21) 0 0.59 (1.33) 0 0.58 (3.48) 0 (0.3) 0.29 (1.0) Doliolids 0.85 (1.93) 0.07 (0.23) 1.87 (0.51) 0.94 (0.62) 4.10 (7.19) 3.32 (5.66) 0.27 (0.48) 0 3.55 (1.34) 2.12 (4.25) 0.58 (0) 0.58 (0.4) 1.04 (6.9) Appendicularia 9.52 (5.07) 1.90 (1.93) 11.23 (12.11) 0.75 (0.83) 9.42 (0.89) 12.17 (14.21) 5.60 (9.41) 16.35 (13.03) 7.69 (8.36) 0 5.81 (3.48) 20.96 (16.8) 17.03 (11.8) Fish egg 0.95 (0.69) 0.74 (0.65) 0.83 (2.1) 0 (0.62) 0.30 (1.08) 0 (0.20) 3.7 (2.28) 0 0 0 2.91 (0) 0 0.74 (0.68) Fish larvae 0.56 (0.48) 0.92 (0.16) 0 (1.67) 0 0 0 1.37 (2.13) 0 (1.40) 0 (0.67) 0 0 0 0.15 (0)
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Table 3. Comparison of Total mean abundacne (Ind.m-3) and % Occurrence of mesozooplankton at four stations.
HS OC HBM SBM Ind-m-3 % Occurrence Ind-m-3 % Occurrence Ind-m-3 % Occurrence Ind-m-3 % Occurrence Coelentrate 4200 0.53941545 11033 1.4170358 1766.7 0.22689697 1733.3 0.2226159 Ctenophores 200 0.02568645 300 0.0385297 133.33 0.0171243 533.33 0.0684972 Nematods 5500 0.70637737 3066.7 0.3938589 12133 1.55831129 4333.3 0.5565397
Polychaete larvae 35600 4.57218808 23033 2.9582228 16867 2.16622394 16933 2.1747861 Marine planktonic worms5533.3 0.71065845 2.0817 0.0002674 700 0.08990257 2233.3 0.286832 Gastropods 3700 0.47519932 4933.3 0.6335991 3466.7 0.4452318 2900 0.3724535 Bivalves 2000 0.2568645 5700 0.7320638 3300 0.42382642 1800 0.231178 Nauplii 37167 4.77339861 37500 4.8162094 27733 3.56185439 19433 2.4958667 Zoea 25567 3.28358451 31967 4.1055509 10300 1.32285217 10933 1.4041926 Mysids 3166.7 0.40670212 3200 0.4109832 300 0.03852967 766.67 0.0984647
Lucifers 2133.3 0.2739888 3033.3 0.3895778 1366.7 0.17552407 866.67 0.1113079 Cladocerans 61067 7.84292937 127700 16.400798 40300 5.17581966 33300 4.2767939 Ostracods 4100 0.52657222 2566.7 0.3296428 2200 0.28255095 3900 0.5008858 echinoderm 866.67 0.11130795 333.33 0.0428107 133.33 0.0171243 66.667 0.0085621 Chaetognatha 4600 0.59078835 6533.3 0.8390907 3766.7 0.48376147 6266.7 0.8048421 Salpas 866.67 0.11130795 900 0.115589 800.67 0.10283142 966.67 0.1241512 Doliolids 2000 0.2568645 4316.7 0.5543992 2800.7 0.35969592 3266.7 0.4195453 Appendicularia 25200 3.23649269 17000 2.1833482 7167.2 0.92050247 12900 1.656776 Fish egg 2000 0.2568645 4966.7 0.6378802 933.33 0.1198701 666.67 0.0856215 Fish larvae 1433.3 0.18408622 3333.3 0.4281075 233.33 0.02996752 100 0.0128432 29
Table 4. Comparison of total copepods mean density at surface and 5m waters (Ind. m-3) from four stations.
HS OC HBM SBM S 5m S 5m S 5m S 5m Sept.12 16533.33±288.67 12166.66±1021.43 10000±458.25 13033.33±208.16 16166.66±2307.23 7800±400 6033.33±550.75 9033.33±305.5 Oct 25700±2515.94 53766.66±7579.13 30366.66±1550.26 29433.33±1361.37 8866.66±1096.96 14000±2029.77 1366.66±230.94 1433.33±152.75 Nov 2300±400 5933.33±305.50 5533.33±723.20 26500±781.02 1600±346.41 533.33±152.75 2800±173.20 1166.66±152.75 Dec 2600±435.88 12766.66±1101.5 11666.67±251.66 17300±721.11 5200±435.8 16333.33±1656.30 6100±624.49 12433.33±568.62 Jan 9133.33±1625.83 20700±624.499 1666.66±378.59 10366±1234.233 2033.33±230.94 3000±346.41 5900±655.74 4033.33±351.18 Feb 4900±721.11 9666.66±585.94 8100±100 10000±500 5233.333±152.75 7533.33±321.45 1233.33±152.75 1400±264.57 Mar 8366.66±709.45 12466.67±757.8 5633.33±305.50 8533.33±665.83 9966.66±1137.24 24200±1587.45 11933.33±152.75 9500±100 Apr 3466.66±230.94 4366.66±896.288 5400±556.77 3633.33±665.83 3800±556.77 2866.66±802.08 3700±435.88 3066.66±1011.599 May 4533.33±115.4 13300±600 4533.33±378.59 18166.66±1205.54 12033.33±208.16 5900±264.57 36000±2553.42 28733.33±2804.16 Jun 50±70.71 100±100 166.66±57.73 266.66±57.73 166.66±57.73 300±100 0 166.66± 152.75 Jul 4066.66±450.92 2200±458.25 5500±624.49 2866.66±251.66 1100±100 3733.33±611.010 3766.66±550.75 1300±173.205 Aug 7600±200 20900±888.81 15800±435.88 8933.33±611.01 1000±173.20 200±100 1933.33±461.88 4600±435.88 Sept.13 6100±556.77 9033.33±305.50 4733.33±650.64 4033.33±450.92 1466.66±416.33 3166.66±251.66 4200±346.41 5000±346.41
30
Figure 7. Seasonal Shannon-Wiener Diversity Index (Hˈ) and species richness (d) at HS, OC, HBM and SBM.
31
Figure 8. Mean density of the MZ community groups at studied stations during September and October (2012) at surface and 5m (Ind. m-3) depth.
32
Figure 9. Mean density of the MZ community groups at studied stations during November and December (2012) at surface and 5m (Ind. m-3) depth.
33
Figure 10. Mean density of the MZ community groups at studied stations during January and February (2013) at surface and 5m (Ind. m-3) depth.
34
Figure 11. Mean density of the MZ community groups at studied stations during March and April (2013) at surface and 5m (Ind. m-3) depth.
35
Figure 12. Mean density of the MZ community groups at studied stations during Mary and June (2013) at surface and 5m (Ind. m-3) depth.
36
Figure 13. Mean density of the MZ community groups at studied stations during July and August (2013) at surface and 5m (Ind. m-3) depth.
37
Figure 14. Mean density of the MZ community groups at studied stations during September (2013) at surface and 5m (Ind. m-3) depth.
Figure 15. Comparison of copepods and mesozooplankton (MZ) annual % of occurrence at HS, OC, HBM and SBM.
38
Figure 16. Variation in total abundance (Ind-m-3) within MZ and copepods.
Figure 17. Comparitive abundance of MZ (Ind-m-3) at HS, OC, HBM and SBM.
39
3.3. EFFECTS OF ENVIRONMENTAL VARIABLES ON MESOZOOPLANKTON (MZ)
Relationship between physical parameter and MZ were analysed through linear regression analysis. Cladoceeran showed significant relation with temeperature at HS and SBM. Cladoceran high significance with salinity at OC (R2=24.8%, P=0.083) and HBM (R2=25.6%, P=0.077). Geliteneous zooplankton expressed high significant relation (HS, R2= 48.2%, P= 0.008; OC, R2= 32.2%, P= 0.043; SBM, R2=40.2%, P= 0.02) with temperature at all stations except mangrove. Nematodes showed highly sinificant relation with salinity at OC and HBM, R2=29.3%, P=0.056; R2=22.4%, P=0.102 respectively. Polchaetes larvae showed significant relationship with salinity at HBM (R2= 21.6, P=0.11) and with Chl a at HS and OC (Tabe 5).
The cluster analysis (CA) shows similarities between different MZ groups (Figure 18- 19). The CA indicates the formation of three groups. The nauplii, zoea, polychaete larvae and appendicularia group together at both HS and OC (Figure 18). Ctenophores, other planktonic worms and echinoderm larvae were the least abundant group at all stations (Figure 18 and 19). The MZ clustered in five groups at both HBM and SBM (Figure 18). The CA of HBM shows separate grouping of nauplii, polychaete larvae, and cladoceran. Whereas, chaetognath and appendicilarian shows affinity with zoea in contrast to SBM where chaetognath show closeness to zoea and appendicularian was close to naupli (Figure 19).
Figure 21 shows the MDS ordination based on MZ abundance in relation to monsoon season. Variations were observed in MZ with respect to monsoon season. The MZ abundance shows close resemblance (80 %) between SWM and NEM at all four stations. The less abundance resemblance of MZ was recorded in POM at SBM. 80% similarity was noted between HS and SBM during SWM seasons. During NEM high resembles was noted between HS and mangrove stations (Figure 22).
40
Table 5. Linear regression analysis and one-way ANOVA (P < 0.05) for zooplankton groups with four predictor variables at all four stations.
41
HS
Fish egg Cnidaria s Salpa p
u Ostracods
o
Lucifers r
Chaetognatha g Fish larvae
n Nauplii
o
Polychaete larvae t
Appendicularia k
Zoea n
a
Cladocera l
Mysids p
Bivalve larvae o
Gastropod larvae o
Doliolids z
Nematods o
Echinoderm larvae s
Marine planktonic worms e
Ctenophora M 20 40 60 80 100 Similarity
OC Doliolids
s Ostracods
p Nematods
u Salpa
o
Fish larvae r
Fish egg g Chaetognatha Gastropod larvae n
o
Bivalve larvae t
Cnidaria k
Zoea n
Polychaete larvae a
l Appendicularia
p Nauplii
o Lucifers
o
Cladocera z
Mysids o
Echinoderm larvae s
Ctenophora e
Marine planktonic worms M 20 40 60 80 100 Similarity Figure 18. Results of Bray-Curtis cluster analysis among MZ groups showing similarity in abundance at HS and OC.
42
HBM
Fish larvae Mysids s Echinoderm larvae p
u Ctenophora
o
Lucifers r
Marine planktonic worms g
Salpa
n Nauplii
o
Polychaete larvae t
Cladocera k
Nematods n
a
Doliolids l
Ostracods p
Fish egg o
Appendicularia o
Chaetognatha z
Zoea o
Bivalve larvae s
Gastropod larvae e
Cnidaria M 40 60 80 100 Similarity
SBM Marine planktonic worms
s Ctenophora
p Echinoderm larvae
u Salpa
o
Cnidaria r
Doliolids g Bivalve larvae Nematods n
o
Cladocera t
Polychaete larvae k
Chaetognatha n
Zoea a
l Appendicularia
p Nauplii
o Ostracods
o
Gastropod larvae z
Fish egg o
Lucifers s
Mysids e Fish larvae
M 20 40 60 80 100 Similarity Figure 19. Consequences of Bray-Curtis cluster analysis of MZ groups showing similarity in abundance at HBM and SBM.
43
Figure 20. Mesozooplankton similarity between stations based on Bray-Curtis similarity matrix.
Figure 21. MDS ordination based on MZ abundance and monsoon season showing 80% resemblance between SWM and NEM at HS, OC and mangrove stations HBM and SBM.
44
Figure 22. (a) MDS ordination based on seasonal distribution and similarities between the stations in terms of MZ abundance at 4 stations during 4 monsoonal seasons (b) close view.
45
3.4. MESOZOOPLANKTONS AND CHLOROPHYLL RELATION
The phyto-zooplanktons relation was estimated throughout the study period at all stations by analysing chlorophyll a concentration in the water.
3.4.1. PHYTO-ZOOPLANKTON RELATION AT HS and OC
The classical relation (inverse relation) among phytoplankton and zooplanktons were evaluated at HS and OC. At both stations the lowest concentration of Chl a (0.02 mg.m-3) and the highest count of MZ was recorded in October. Early SWM months showed very low abundance of MZ (May and June) but the highest peak of phytoplankton biomass was recorded at HS during May and June, 49-43 mg.m-3 respectively (Figure 23).
At OC, during September to November the low Chl a and high MZ were estimated. Whereas the high Chl a was estimated during May, June and August 2012 and the same months reflected the low MZ abundance at OC. The similar pattern between MZ and Chl a was noted during January to March 2013 (Low Chl a and high MZ) (Figure 23).
3.4.2. PHYTO-ZOOPLANKTON RELATION AT HBM and SBM
Mangrove site HBM showed negligible difference among MZ and Chl a concentration during November 2012, January, April and July 2013.The highest concentration of Chl a was recorded during December. The high inverse relation were observed during September 2012 where low Chl a and high MZ were observed. June and September 2013 were with decline in MZ with peaks concentration of Chl a (Figure 23).
Mangrove site SBM showed slightly different pattern of Chl a and MZ annual distribution. Chl a and MZ were in inverse relation during September 2012 and both were low during October 2012. Similar pattern was noticed during April and July 2013. Highest Chl a concentration were recorded during May and June 2013 with the lowest MZ (Figure 23).
46
Figure 23. Comparative variation in zooplankton total mean abundance (Ind. m-3) with Phytoplankton biomass (Chl a mg m-3).
47
4. DISCUSSION
Northern Arabian Sea receives the effect of Asian monsoonal influence which not only effects the hydro chemical and physical changes but also reported to influence the primary productivity of the region (Kumar et al., 2001). Typically bio-physical and chemical processes in mangrove ecosystems are highly influenced by the availability of fresh water.
The present study was conducted to evaluate the density and composition of MZ and effects of physico-chemical factors on MZ community structure. In this study the MZ composition of mangrove forest was compared with the MZ composition of other two sites, one site is receiving pollution effects (HS) and other site get influence from open ocean (OC). A rise in temperature and salinity was noted when the data was compared with earlier reports. Qasim, 1982 reported temperature range 22.55 - 28.5 oC and salinity 36.02 - 36.74 ppt. The results of present study indicates the facts of rising Temperature and Salinity (19.6 - 33.7 oC and 30-45ppt) in the coastal waters of Pakistani since 1982. The higher temperature results in high salinities (Williams 2001). Similar results were given by Cornella Jsapers et al., 2009. Comparatively low salinities were recorded at SBM and HS as these stations receive flow from Layari River which include domestic and industrial waste (Beg et al., 1984, 1992). Nutrient rich environment promotes the phytoplankton production in ecosystem (Parab et al., 2006). Chl a play role as an indicator and estimator of phytoplankton biomass (Harris, 1986). During current study higher concentration of Chl a were observed during December and May as compare to earlier studies in which the higher Chl a values were reported from June (Naz, et al., 2013; Saifullah, 1994). The occurrence of Noctiluca scintillans blooms was reported from December to March 2013 (Chughtai and Saifullah, 2006) and the presence of the blooms of this species is the possible cause of high Chl a concentration during December. The blooming conditions of N. scintillans were also reported as green phenomena in during winter season (NE monsoon) from other areas of the region (Devassy and Nair, 1987., Subrahmanyan, 1954).
The structure of MZ community in ecosystem and their numerical abundance is reported to be strongly influenced by the abiotic and biotic factors (McFarland et al., 1985;
48
Cocheret de la Morinière et al., 2004) and the residents of the specific ecosystem defines the quality of the ecosystems as favourable conditions increase the numerical abundance of inhabitants. Mangroves extensive root system was reported to provide shelter and food to wide variety of organisms and they are considered as the nutrient rich environment (Alongi, 2002). Mangrove are the nursery grounds for meroplanktons which exhibit short time as planktons in the early stages of their life. Although the density of MZ were low at mangrove stations but ther are rich in mesozooplankton diversity specially in summer season.The low abundance of MZ and copepods at mangrpve stations as compare to the other stations (HS and OC) might be due to the predation and turbid conditions although the high phytoplankton biomass at mangrove stations indicates the presence of rich food supply. MZ in mangroves ecosystem are the main source of trophic interaction (Godhantaraman 2001). The zooplanktons was the preferable food item for the many species invertebrates and fishes). High survival rate of zooplanktons found in the nutrient rich, less predation site and favourable environment (McFarland et al., 1985; Cocheret de la Morinière et al., 2004).
Coastal waters were reported as high productive environments in view of food supplies (Cebrián and Valiela, 1999). That explain the high abundance of MZ at OC.
HS receives the influence from the Layari river discharge in terms of high organic waste. This explains the presence of detritivorus and opportunistic feeders such as polychaete larvae, appendicularians and other identified planktonic worms at this station. Polycheates are the bio-indicator species of environment change. This concept has been establied earlier research with respect to their response to envoirnmental flucuation (Maurer et al., 1988; Dean, 2004). The high occurrence of polycheate larvae at HS indicates the availability of food and polluted environment with respected to organic pollution.
Penilia avirostris is the most abundant cladoceran in the present study and has been reported frequently from coastal waters (Della Croce and Venugopa,l 1973; Grahame, 1976). The concentration of Chl a was low when the cladocerans were high in abundance which indicates the consumption of the extensive part of primary productivity by this species as reported by other scientists (Bosch and Taylor, 1973; Turner et al., 1988; Kim et al., 1989). The fluctuation in temperature is reported to effect the occurrence of 49
cladocerans (Marazzo and Valentin, 2004). The cladoceran abundance was low during the high temperature months and Penilia avirostris was the only representative of this group in the summer sampling of MZ. This species was reported to be frequently found in summer season in marine environment from other parts of the oceans (Ramirez, 1985; Onbé and Ikeda, 1995).
During study increased abundance of nematodes were recorded from May to June. Similarly summer abundance of nematodes were reported from Southern North Sea by Vanaverbeke, et al., 2004. Nematodes showed their dominancy during summer at HS and HBM. The availability of organic waste and microalgae has been reported to promote the high abundance of nematodes (Palmer 1983; Bertelsen 1997; Ingels et al., 2009; Powers 1998; Christine et al., 2015). Nutrient recycling and primary production within the mangrove food web is interminable process during all seasons (Clough et al., 2000). Tidal fluctuations transfer the energy in and out of mangrove forest sites HBM and SBM. The mangrove litter is the major source of demineralized nutrient from the litter (Ake- Castillo et al., 2006) which give the sufficient feed in the form of microalgae to increase the density of nematodes. The high Chl a at mangrove stations indicates the presence of epi-growth feeder nematodes at HBM. HS receives organic waste from the Layari River discharge which might also supports the detritus feeder nematods.
Lucifers are the marine meroplankton that exhibit carnivore zooplankton behaviour. The voracious animal feeding behaviour play important role in pelagic prey population within the food web (Hopkins et al., 1993). They contribute in food web trophic interactions in tropical waters (Rajagopalan et al., 1992). Abundance of Lucifer already have been reported from Indian waters (Haridas, 1982, Antony et al., 1990). Lucifer were completely absent from May to July which indicates the scarce food supply which results in the demise of the group because of their fast ingestion rate and short life span due unfavourable conditions (Lee et al., 1992).
Chaetognaths are strictly associated with the physical water parameters which makes them specific to the water masses (Pierrot-Bults and Nair 1991). The abundance of chaetognaths in March at SBM might be linked to the high abundance of copepods. The abundance of copepods indicates the availability of bulk of food to chaetognaths as chaetognaths were reported to feeds on copepods and some fish larvae so they are the key 50
factors in sizing the icthyoplankton and zooplankton communities (Casanova, 1999). The low abundance of Chetognathes in POM and NEM (1.14%) might be due to the lower temperatures as cold season is reported to be the unfavourable season for Chaetognaths worldwide (Itoh et al., 2003). The abundance of fish egg and larvae during pre-monsoon season indicates the fish reproduction season.
Copepods are the most abundant taxa among MZ. Previous reports designate copepods as the major constituent of MZ and their abundance shows fluctuation with tidal currents and other environmental factors (Dur et al., 2007; Gaudy, 2003; Calbet et al., 2001; Dalal and Goswami, 2001). The high density of copepods at HS was due to the presence of small size copepods.
Predation effects the MZ community dynamics and the decline of zooplankton population might be because of the high predation factor (Hassel, 1986). The dominancy of MZ in mangrove waters in summer has been reported earlier (Robertson et al., 1988; Naz et al., 2015). Species richness and the MZ seasonal abundance was related with warm seasons especially in estuarine waters (Dauvin et al., 1998; Junior et al., 2007; Rawlinson et al., 2005). Comparatively lower abundance of MZ was reported from Manora channel by Tahira and Nayeem, 1996.
The seasonality effect was seen between the seasons at all stations. The biomass, abundance and diversity of zooplankton were found to be high during SWM seasons. From Arabian Sea the same pattern validate our statement about the seasonality effect (Smith et al., 1998)
Zooplankton grazing and rich nutrient supply have strong consequence with the phytoplankton bloom. (Officer et al., 1982, Hily 1991, Mellina et al. 1995, Prins et al., 1995). Zooplanktons and phytoplankton are forcefully dependent on each other with inverse interaction (Harvey et al., 1935, Hardy 1936). Variation in this relationship in estuarine areas. The classical interaction between phytoplankton-zooplankton has been reported by several authors in the past (Soreide et al., 2010; Chiba et al., 2008; Broms and Melle 2007; Islam et al., 2006; Baier and Napp 2003; Madsen et al., 2001).
51
Zooplankton community structure, phytoplankton abundance environmental parameters, water current and tides play important role in this relationship. The present study favours the strong coupling between phytoplankton and mesozooplankton.
5. CONCLUSIONS
The high density of MZ were recorded during present study. The MZ displays vertical variations and 5m waters were densely populated as compare to surface waters with few exceptions. The stations shows variations in MZ abundance. Total MZ and copepod abundance were high at OC and HS as compare to mangrove sites. Seasonal pattern showed the SWM abundance in contrast to the other seasons. The density of MZ at stations might be linked to the availability of food and predation. The high Chl a at mangroves sites indicates the high productivity. Temperature, Salinity and chlorophyll a and monsoon appears to regulate the MZ abundance at studied sites.
52
Chapter 3 COPEPODS COMMMUNITY STRUCTURE IN SHALLOW, MANGROVE WATERS IN NORTHERN ARABIAN SEA
53
ABSTRACT
The density and diversity of copepods were estimated belongs to 21 families of calanoida 17 families of cyclopoida and 3 families of harpacticoida at mangrove and non-mangrove stations of Manora channel. A total of 69 species were recorded. The calanoida was dominated (61%) among total copepods. In this study occurrence and abundance of 23 copepods species were described first time from the coastal waters of Pakistan. Highest species diversity was found at HS during October 48 species were present out of 69. A total of 135092 individuals per annum was recorded from HS. HS was followed by OC, HBM and SBM with 127500, 76433 and 82516.6 individuals per annum respectively. The highest density was obtained during SWM season as compare to PRE, POM and NEM. Temora was the most abundant genus at all stations. Significant relation between stations with respect to Temora density was noted. In cyclopoids the Corycaeus genus was most abundant and within harpacticoid Euterpina acutifrons was the most abundant species during this study. For the first time 23 copepods species were reported first time from coastal waters of Pakistan.
54
1. INTRODUCTION
Zooplankton density, population and community structure is reported to be influenced by many physical and biological parameters. In unstable marine habitats, like mangrove forests, the tidal interaction is the main factor (McLusky and Elliott 2004). Not only seasonal and annual variation exhibit in zooplankton community but the diel vertical migration also effects their abundance (Hays, 2003).
Among zooplankton, copepods is the most abundant and dominant group found widely in Ocean including estuarine waters where they contribute 60-80% of the biomass (Hajisamae and Chou, 2003). With respect to the zooplankton population mangrove and coastal areas has been recognised as the densely populated areas (Robertson and Blaber, 1992; Uye et al., 2000; Renz et al., 2008; Vinas et al., 2002). Copepods forms the biggest population in the ocean like insects on earth (Humes, 1994; wiebe et al., 1982). Copepods consist of 10 orders, 11500 known species belonging to 198 families and 1600 genera (Humes, 1994).
Calanoid copepods have the dominant position in copepods and their daily diel vertical movement from up to down and from down to top transfer organic matter, thus playing crucial role in biological pumping and nitrogen revival (Leon and Ikeda 2005; Kobari et al., 2008; Richardson, 2008). Consumption of organic matter from microbial loop has been attributed to copepods (Champalbert and Pagano, 2002; Sommer and Stibor, 2002; Turner, 2004). The role of copepods in nutrient cycling, carbon flow and transformation of energy within the food web is well established (López- Ibarra and Palomares-García, 2006). Copepods transfer energy from primary producer to the primary consumer and at upper levels of food chain (Leandro et al., 2014; Richardson 2008; Faure, 1951) and they act as an indicator of biodiversity. According to feeding strategies and habits the copepods are either herbivore or carnivore, but mainly they are considerd as omnivores (Mullin, 1966; Paffenhofer and Knowles, 1980).
Sensitivite copepods species response to envoirnmental issues, which helps in ecosystem management (Tseng et al., 2008). Abundance and distribution of copepods in marine envoirnment play important economic role in controlling fisheries stock (Uye et al., 2000). Shellfisheries and many other pelagic fishes of high economic worth consequently 55
depends on the density of copepods population (Beaugrand et al., 2003; Marcogliese, 2002; Conover et al., 1995).
The dynamics of estuarine ecosystem depends on the physico-chemical charachteristics of the water body (Elliott and McLusky 2002; Hitchcock et al., 2002), such as eutrophication, which leads to the environmental changes within ecosystem (Suikkanen et al., 2013). Climate and seasonal driven environmental changes in marine envoirnment strongly effect the community structure of mesozooplankton. Copepods have a vast range of distribution and they act as indicators of environmental disturbances in ecosystems. The variation in biological parameters such as the availability of food, risk of predation and physical parameters effect the ontogeny and population density of the copepods. (Escribano and Hidalgo, 2000; Beyst et al., 2001). In mangrove and other marine ecosystem, the seasonal occurrence and abundance of copepods was was reported to be influenced by salinity, osmoregulation and habitat tolerance (Ara, 2004; Uriarte and Villate, 2005).
The knowledge about the marine zooplankton species diversity and abundance in western Indian Ocean has been confined mostly to the large sized copepods (Gallienne and Robins, 2001), and only limited information about copeodes species diversity and abundance from Arabian Sea were available. From Arabian Sea, earlier efforts regarding the qualitative and quantitative work on copepods has been done by Sewell, 1929, 1932 and 1948, Seno, 1962; Voronina,1962; Decker et al., 1965, Grice and Hulseman, 1967; Fleminger, 1973; Kasturirangan et al., 1973. The major attention has been given to the large size calanoid copepods in terms of diversity and abundance, whereas, the smaller copepods suh as cyclopoid received less endeavour. Cyclopoid copepods play important role in the marine ecosystem by being the important grazer on phytoplankton (Fransz and Gonzalez, 1997) and information on this group provide important information about the zooplankton–phytoplankton intractions.
Prior to the distribution and abundance, correct identification is most important step in the analysis of copepods diversity. Earlier research on zooplankton from Pakistani waters were contributed by Masihuzzaman, 1973; Haq et al., 1973; Ali-Khan and Hempel, 1974; Ali-Khan and Ali-Khan, 1978; Muniza and Kazmi, 1995; Naz et al., 2012. The work on copepods abundance and community structure were limited up to the group level. Very 56
limited information regarding species abundance were available in literature (Haq et al., 1973, Khan, 1974 and 1979). Haq et al., 1973 give the abundance of 16 copepods species from Pakistani coastal waters. The taxonomic account of calanoid copepods was given by Khan, 1979 in which seasonal abundance of 11 calanoid species was discussed from Manora channel. Khan, 1998 give only taxonomic description of 55 calanoid copepods and since then, no work has been done on the species diversity and abundance of copepods.
The aim of the present study is to enhance the knowledge about copepods species diversity, abundance and seasonal distribution in coastal waters of Pakistan. Monsoonal reversal of currents creates unique seasonal driven changes in Arabian Sea which might effects the copepods community residing in the area. In present study calanoid, cyclopoid, harpacticoid and monstrilloid copepods were identified up to the species level and the effect of monsoon on the density and distribution was evaluated.
57
2. MATERIAL METHODS
2.1. COLLECTION SITES
Copepods collection was carried out at all four sampling sites as described in Chapter, 2.
2.2. FIELD SAMPLING
2.2.1. COLLECTION AND ANALYSIS OF PHYSICOCHEMICAL PARAMETERS
Refer to chapter2.
2.2.2. COPEPODS SAMPLING AND HANDLING
Quantitative sampling was conducted by using zooplankton net with net diameter 0.29 m and mesh size 170 micron (See Chapter 2 for details). For identification and counting of copepods, aliquots were made to erase the error in counting the zooplankton population. 3 aliquots (each 10ml) were made for each sample. After subsampling the aliquots were transferred with the help of glass pipette to Sedgewick-Rafter cell for complete counting. Each sample was sorted and copepods were separated by using steriomicroscope and transferred to separate vials. Further sorting and identification of specimen up to family, genus and species level was done by using stereomicroscope and digital microscope (Optika B-290 T).
2.2.2.1. TAXONOMIC STUDY OF COPEPODS
To minimize the risk of misidentification the dissection and complete taxonomy was performed for most of the specimens. Specimen for identificantion were preserved in 50 % glycerine. Species identification was made possible with the help of previously cited literature (Nishida, 1985; Mackinon, 2000; Al-Yamani et al., 2011; Razouls et al., 2005–
58
2016). Annual and seasonal abundance of copepods was estimated by following the ICES zooplankton methodology manual (Harries et al., 2000). After identification the species abundance was calculated in ind- m-3.
Scheme for the basic identification of copepods viewing ventral and lateral side (Hugget & Bradford-Grieve 2007) 59
2.3. STATISTICAL ANALYSIS
One-way ANOVA and regression analysis was performed to analyse the habitat relation and density variation in copepods abundance. Five frequently found calanoid genus and two genus of cyclopoids and one from herpacticoids copepods was slected to check the variation in density among mangrove stations and between mangroves with non- mangrove stations. For the evaluation of similarity in seasonal abundance of copepods, the cluster analysis was performed on Bray-Curtis similarity matrix. Shannon diversity index and species richness was calculated at all four stations.
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3. RESULTS
A total of 69 species of copepods which belongs to 4 orders 21 families were identified. Copepods was represented by 4 orders. Calanoid was the most dominated (61 %) and Monstrilloid (1.2 %) were the least abundant (Figure 1). Diversity indices was performed for copepods species (Table 1). High diversity of copepods was recorded high from non- mangrove stations. At HS mean value of H’ was 2.36 ± 0.698 and at HS 2.33 ± 0.859 respectively. Highest number of species (48) were recorded at HS during October. From HS and OC stations highest number of species was recorded during October. From Mangrove stations HBM (29) and SBM (23) high species was recorded in September 12. High species richness was recorded at HS during October.
Figure 1. Comparison of occurrence (%) of the four orders of copepods.
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Table 1. Comparison of copepods diversity index, evenness and richness at all stations.
S12 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug S13 Species nubers (S) 41 48 16 27 25 19 23 26 18 2 15 15 29 Total abundance of species (N) 33033 71967 7067 14100 27433 12500 17333 6300 17967 367 5233 23133 14033 Richness (d) 3.844 4.202 1.692 2.721 2.348 1.908 2.254 2.858 1.735 0.1694 1.635 1.393 2.932
HS Evenness (J') 0.7724 0.806 0.7109 0.8976 0.8176 0.7079 0.8699 0.8704 0.7419 0.8454 0.8648 0.6023 0.8536 Shannon Diversity Index (H') 2.869 3.12 1.971 2.958 2.632 2.084 2.728 2.836 2.144 0.586 2.342 1.631 2.874 Mean H' 2.36 ± 0.698 Species nubers (S) 30 45 22 31 19 19 16 27 18 1 10 24 21 Total abundance of species (N) 22033 58967 30733 25400 11533 17200 9867 7700 21500 133 7833 16900 8200 Richness (d) 2.9 4.006 2.032 2.958 1.925 1.846 1.631 2.905 1.704 0 1.004 2.363 2.219
OC Evenness (J') 0.7905 0.8526 0.6796 0.9134 0.6926 0.5447 0.9417 0.941 0.7977 0 0.8606 0.8936 0.8658 Shannon Diversity Index (H') 2.689 3.245 2.101 3.137 2.039 1.604 2.611 3.101 2.306 0 1.982 2.84 2.636 Mean H' 2.33 ± 0.859 Species nubers (S) 29 28 11 22 14 18 26 22 18 3 12 4 15 Total abundance of species (N) 18182 22367 2000 14033 5233 11200 29933 5533 17967 433 4233 367 4433 Richness (d) 2.855 2.696 1.316 2.199 1.518 1.823 2.426 2.437 1.735 0.3294 1.317 0.5081 1.667 Evenness (J') 0.846 0.782 0.883 0.9173 0.8282 0.7644 0.8315 0.8119 0.6993 0.7817 0.9041 0.895 0.8161 HBM Shannon Diversity Index (H') 2.849 2.606 2.117 2.835 2.186 2.209 2.709 2.51 2.021 0.8587 2.246 1.241 2.21 Mean H' 2.199 ± 0.584 Species nubers (S) 23 7 11 21 15 9 17 16 19 3 10 10 22 Total abundance of species (N) 15400 2800 3633 16733 9067 2800 17767 5750 38867 101 4933 4533 7467 Richness (d) 2.282 0.7559 1.22 2.057 1.536 1.008 1.635 1.733 1.703 0.4338 1.058 1.069 2.355 Evenness (J') 0.7726 0.9159 0.804 0.8915H1H25:Y270.7974 0.7546 0.8948 0.8915 0.5027 0.6082 0.846 0.8536 0.8739 SBM Shannon Diversity Index (H') 2.423 1.782 1.928 2.714 2.16 1.658 2.535 2.472 1.48 0.6682 1.948 1.965 2.701 Mean H'2.033 ± 0.571
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3.1. COPEPODS DENSITY AND DISTRIBUTION
The density of genus in recorded families was estimated to discover the dominant family within the study area. Quantitative analysis reveals family Temoridae as the most abundant family. Family Paracalanidae and family Pontellidae were rich in species. Both families were represented by 3 genus and 9 species in Paracalanidae and 6 species in Pontellidae respectively (Figure 2). Acrocalanus was the most dominant genus in family Paracalanidae. Within the order cyclopoida 4 families were identified. Family Corycaeidae was the dominant family in present study. The Family Oithonidae was represented by 8 species of the genus Oithona (Figure 3). Saphirina and Copilia were the less abundant cyclopoid. Three families of the order harpacticoida; Ectinosomatidae; Euterpinidae and Clytemnestridae were represented by single species. Famiy Euterpinidae was the most abundant harpacticoide family and Euterpina was the most abundant genus (Figure 4).
Monthly mean density of all orders of copepods is given in Table 2. Throughout the study highest number of herpacticoids were recorded in October at OC 2166 Ind-m-3 ± 416.3and 2633 Ind-m-3 ± 152.7 in both surface and 5m waters respectively. Cyclopoid showed highest density during May at SBM 32200 Ind-m-3 ±2455.6. Highest density of calanoid were recorded during October at HS in 5m waters 51366 Ind-m-3 ±7335.7 (Table 2).
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Figure 2. Variation in total average abundance (Ind-m-3) of 19 genus in 13 families of the order calanoida. 64
Figure 3. Average abundance of (Ind-m-3) 4 cyclopoids families and 5 genus.
Figure 4. Average abundance (Ind-m-3) of the families and genus of harpacticoida and Monstrillloida.
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Table 2. Group mean abundance and vertical distribution of the copepods at all stations during September 12 to September 13.
Calanoida September October November December January February March April May June July August September S 14166.66±351.18 22033.33±1913.98 1533.3±251.6 866.6±208.1 5900±200 3133.3±404.1 2366.6±404.1 1833.3±115.4 1333.3±152.7 50±70.71 3533.3±568.6 5866.6±208 3800±400 HS D 9733.33±802.08 51366.66±7335.7 3733.3±251.6 7466.6±709.4 14300±655.7 7300±556.7 4333.3±1159.0 1666.6±305.5 3900±264.5 100±100 1966.6±450.9 19200±1058.3 7466.6±611.01 S 12266.6±1078.5 7166.6±568.6 500±100 2933.3±305.5 1033.3±152.7 2566.6±404.1 3700±721 1200±200 3566.6±208.1 166.66±57.7 1100±100 900±100 1233.3±305.5 HBM D 6833.3±305.5 11866.6±2003.3 366.6±152.7 7600±1135.7 1300±200 4566.6±550.7 10300±781 566.6±251.6 1000±200 133.3±115.4 3733.3±611 133.33±57.7 2600±360.5 S 7533.3±737.1 24033.3±212.1 3733.3±305.5 5866.66±152.7 533.3±251.6 6833.3±251.6 2333.3±305.5 2800±600 400±100 0 5100±655 12366.66±776.7 3466.6±650.6 OC D 8166.6±702.3 23966.6±1050.3 20100±953.9 9533.3±709.4 8100±1178.9 8500±529.1 2933.33±208.1 1933.3±702.3 5766.6±208.1 133.3±57.7 2800±300 7200±529.1 3500±500 S 4766.66±1123.9 666.6±152.7 1233.33±152.7 2766.6±351.1 3166.66±351.1 966.6±152. 5100±300 1066.6±57.7 3000±100 0 3766.6±550.7 1700±360.55 3633.3±351.1 SBM D 7766.66±642.9 1066.6±152.7 400±100 6900±400 2466.66±351.1 966.66±152.7 4766.66±251.6 533.33±57.7 1566.6±208.1 66.66±57. 433.3±152.7 3266.66±665.8 4166.66±435.88
Cyclopoida September October November December January February March April May June July August September S 2000±500 3033.33±802.08 500±100 1633.3±321 2833.3±152.7 1166.6±152.7 5700±264.5 1500±264.5 2966.6±321.4 0 400±100 600±100 1300±100 HS D 1866.66±378.59 1600±435.88 2200±300 4800±400 5500±793.7 2166.66±305.5 6400±458.2 2166.6±503.3 9133.3±321.4 0 233.33±57.7 433.3±57.7 766.6±57.7 S 2366.6±1001.6 933.3±321.4 1100±264.5 1466.6±251.66 1500±173.2 2433.3±208 6000±916.5 2533.3±503.3 8233.3±152.7 0 0 100±100 166.6±57.7 HBM D 866.6±152.7 866.6±321.4 166.6±57.7 8200±818.5 1633.3±351.1 2533.3±152.7 12833.3±1892.96 1933.3±513.1 4833.3152.7 33.3±57.7 0 66.6±57.7 466.6±57.7 S 1333.3±152.7 4166.6±838.6 1633.3±288.67 4966.66±152.7 1000±200 1033.3±152.7 3133.3±351.1 2600±500 3433.3±208 166.66±57.7 0 1633.33±321.4 866.6±115.4 OC D 3100±264.5 2833.3±378.59 5833.3±378.5 6866.66±404.1 1833.3±251.6 833.3±152.7 4766.66±750.5 1666.6±152.7 10700±854.4 133.33±57.7 0 733.3±152.7 533.3±57.7 S 966.66±251.6 700±100 1566.66±208.1 2600±500 2100±360.5 266.66±57.7 6500±300 2533.33±404.1 32200±2455.6 0 0 0 500±0 SBM D 666.66±321 366.66±57.7 700±100 5000±200 1233.33±351.1 133.33±57.7 3466.6±351.1 2033.3±814.5 26666.66±3089.22 66.66±57.7 866.66±115.4 0 400±100
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3.2. SPECIES DISTRIBUTION AND DENSITY 3.2.1. DENSITY OF THE CALANOID COPEPODS AT FOUR STATIONS
Order Calanoida was represented by the 47 species belongs to 19 Genus and 13 families.
Family Calanoidae
Only two species in this family Undinula vulgaris and Canthocalanus pauper were recorded from all four stations. Undinula vulgaris was high in abundance during October at OC (966.66 Ind-m-3). Vertical abundance showed its absence from 5m waters. U. vulgaris was not recorded from mangrove stations (Figure 5). Canthocalanus pauper were recorded high during October from HS and OC (1466.66 and 1433.33 Ind-m-3 respectively). C. pauper was the least abundant specie at mangrove stations and only during March (Figure 5).
Family Paracalanidae
This family represented by 9 species out of which 6 identified species belongs to the genus Acrocalanus. Acrocalanus longicornis was distributed commonly at all four stations. A. longicornis was recorded in high profusion during October at all stations. At HS and OC high abundance from surface and 5m was recorded 2500 Ind-m-3 and 3700 Ind-m-3 respectively. A. gracilis was recorded with high abundance at HS during October 2666 and 7600 Ind-m-3 from surface and 5m waters respectively. A. gracilis was not found at HBM and SBM in surface waters (Figure 6). A. monachus was recorded high in abundance at HS and OC as compare to HBM and SBM. A. monachus was abundant in September, October, December and January. Highest abundance of A. monachus was recorded at HS in 5m waters and OC in surface waters (6500 and 1066 Ind-m-3 espectively). A. gibber was recorded from all stations except HBM. High abundance of A. gibber was observed at HS during October and January from surface and 5m waters respectively. From SBM highest density was recorded in May. Acrocalanus sp. 1 and 2 was found in high density at HS and
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OC during October. Overall the high occurrence of Acrocalanus species was reported to be from October to May. The summer months (Jun, Jul, Aug and Septembers) were the least or zero abundant months for the genus (Figure 6).
Genus Bestiolina stands with 2 species. Bestiolina similis and B. arabicus were noted with high density from August at HS. Both of the species only showed their abundance during August, September, October and December at HS and OC (Figure 7). Mostly both species did not show abundance at HBM and SBM (Figure 7).
The single representative of the genus Paracalanus parvus. P. parvus was recorded high during October and November at HS and OC respectively. At SBM P. parvus was recorded high in abundance during March and May. P. parvus were completely absent during summer months (June to September) (Figure 7).
Family Eucalanidae
The family represent two genus Eucalanus and Subeucalanus. Eucalanus bungii was reported as a single species of the genus. The highdensity of the E. bungii was recorded at OC and HBM in both surface and 5m waters. The species was completely absent at HS and SBM. Peak in abundance was recorded from December in 5m waters at OC (Figure 8a).
Genus Subeucalanus is represented by 4 species and all of these species were present at all stations. Subeucalanus crassus was recorded at HS and OC from September, October, February and April. S. crassus was least abundant at mangrove stations and high abundance was recorded during April (Figure 8b). S. subcrassus was the most abundant species of the genus as compare to other 3 species. Maximum abundance of the S. subcrassus was recorded from surface waters of HS, OC and HBM during October. While in 5m waters peak abundance was recorded during September, October, December and February (Figure 8b). S. pileatus was the inhabitant of all stations from July to September 13. The highest abundance was recorded at SBM and HS during October and December (933.33 Ind-m-3). S. pileatus was not recorded from January to June (Figure 8b). S. subtenuis was recorded at
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mangroves stations in April only. In 5m waters the species was recorded only at OC and HBM during November, December and February (Figure 8b).
Family Rhincalanidae
This family was represented by a single species Rhincalanus sp. This species was only recorded at HS and OC during September, October, November and March from surface and 5m waters and was completely absent at HBM and SBM (Figure 9).
Family Clausocalanidae
This family is represented by one genus Clausocalanus. Two species of the genus Clausocalanus minor and C. furcatus was recorded. C. minor at surface waters was present in high abundance at HS during October, whereas in 5m waters highest density was reported at HS 866 Ind-m-3 (Figure 10). C. furcatus was reported from all stations except BM. High density was reported at HBM during February in surface and 5m waters (333 and 400 Ind-m- 3 respectively) (Figure 10).
Family Euchaetidae
The family was represented by single species, Euchaeta marina and was only reported from OC and HBM during October and November from surface and 5m waters (Figure 11).
Family Centopagidae
The family was represented by single genus and 8 species. Centropages orsinii was reported to be high in density at OC in surface waters during March (1133.33 Ind-m-3). Whereas in 5m waters C. orsinii showed high density at HS (1766 Ind-m-3) in September 13. C. dorsispinatus was highly abundant during September 13 at all stations and was completely absent from February to June (Figure 12a).
C. karachiensis was recorded only from two stations HS and OC. C. karachiensis was present in highest abundance during September 12 at OC (2000 and 933 Ind-m-3 from surface and 5m waters respectively) and was completely absent fro November to August
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.HBM and SBM stations were despicable for the species. From November to August the specie was completely absent. (Figure 12a).
C. tenuiremis was recorded throughout the year from all stations except November, December and June. High density were observed at HS and OC during October (1866 Ind- m-3 in surface waters and 1566 Ind-m-3 in 5m waters).
C. furcatus was abundant during March at HS and HBM in surface waters. Highest density was observed during November at OC (3133 Ind-m-3). Species was recorded from all stations but completely absent at both surface and 5m during December, April, June and August (Figure 12b). C. hamatus showed its highest density at HBM (300 Ind-m-3) during December and was noted to be present during September, October, November, April and August at all stations except SBM. C. alocki and C. calanius were the least abundant species of the genus Centropages. Both of the species were recorded with their highest density at HS during September 12 from surface waters. C. alocki was completely absent from HBM while C. calanius was absent from OC and SBM (Figure 12b).
Family Pseudodiaptomidae
This Family is represented by three species in a single genus. Pseudodiaptomus serricaudatus was the most abundant species in the present study. P. serricaudatus was present with highest density during November at HS and OC. The density of P. serricaudatus from surface waters was 2366 Ind-m-3 and 4366 Ind-m-3 and in 5m waters was 6333 Ind-m-3 and 5666.66 Ind-m-3 at HS and OC respectively (Figure 13). Species were completely absent during June (Figure 13). P. arabicus was present with the high density during October at OC in surface and at HS in 5m depth. The species was absent at SBM throughout the year (Figure 13). P. aurivilli was only noted from HS and OC. This specie was absent at mangrove stations. Highest density was recorded at HS during September 12 (Figure 13).
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Figure 5. Annual vertical varition in mean density (Ind. m-3) of two species of the family calanidae in surface and 5m depth at all stations.
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Figure 6. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Paracalanidae in surface and 5m depth at all stations.
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Figure 7. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Paracalanidae in surface and 5m depth at all stations.
Figure 8a. Annual vertical distribution and mean abundance (Ind. m-3) of the Eucalanus bungii of family Eucalanidae in surface and 5m depth at all stations. 73
Figure 8b. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Eucalanidae at all stations in surface and 5m depth.
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Figure 9. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Rhincalanidae in surface and 5m depth at all stations.
Figure 10. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Clausocalanidae at all stations in surface and 5m depth.
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Figure 11. Annual vertical distribution and mean abundance of the species of family Euchaetidae in surface and 5m (Ind. m-3) depth at all stations.
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Figure 12a. Annual vertical distribution and mean abundance (Ind. m-3) of the 4 species of family Centropagidae at all stations in surface and 5m depth.
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Figure 12b. Annual vertical distribution and mean abundance (Ind. m-3) of the 4 species of family Centropagidae at all stations in surface and 5m depth.
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Figure 13. Annual vertical distribution and mean abundance (Ind. m-3) of the 3 species of family Pseudodiaptomidae at all stations in surface and 5m depth.
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Family Temoridae
Temoridae was represented with three species on the genus Temora. T. turbinata was the most abundant representative of the genus from all studied stations throught the study period. Highest density was noted at OC during February from surface waters (5266 Ind-m- 3) and during November from 5m waters (5766 Ind-m-3). This Species was found continuously from September 12 to May (Figure 14). T. discaudata was highest in abundance at OC 466.66 Ind-m-3 during December in surface waters. At 5m depth this species was high in numbers at OC (900 Ind-m-3) during October and was less abundant at HBM and SBM (Figure 14). The highest density of T. stylifera obsserved at HS and OC during January. The species was completely absent from SBM (Figure 14).
Family Candaciidae
Candaciidae was represented by two species of the genus Candacia. Candacia discaudata were recorded with its high density during October from HS (566.66 Ind-m-3) and HBM (433.33 Ind-m-3) respectively. The species was not recorded during February to September 13. Species was completely absent at OC (Figure 15). Candacia Sp. was not recorded from mangrove stations and highest density was recorded during October (2066.66 Ind-m-3) at OC in 5m waters (Figure 15).
Family Pontellidae
The family was represented by three genus and Calanopia and Labidocera and Pontella. Three species of the genus Calanoipa were identified. Calanopia elliptica was recorded high in density at HS (5433.33 Ind-m-3) during October. This species was only recoded at HS and OC and only present during September 12 and October. C. minor was also recorded only from HS and OC only. From mangrove stations HBM and SBM the genus Calanopia was completely absent. High abundance of the C. minor were recorded at OC during August (366.66 Ind-m-3). The species was only present during October and August (Figure 16a). Calanopia sp. showed the same pattern as others. This species was also recorded high
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during October at HS (2833.33 Ind-m-3) and OC (1533.33 Ind-m-3) in 5m and surface waters respectively.
Two species was recorded under the genus Labidocera. L. acuta showed high abundance during September 13 at OC (333.33 Ind-m-3) in surface waters. Howeve L. acuta were high at HBM (633.33 Ind-m-3) during December in 5m waters and was continuously absent from January to June (Figure 16b). L. pectinata was oftenly observed during sampling as compare to the L. acuta. L. pectinata was recorded in June, July, August and September. Highest density of the species was recorded in August at OC (633.33 Ind-m-3). Pontella securifer was the sole representative of the genus. Pontella seurifer was only reported from OC and SBM in October and August. The peak density (1700 Ind-m-3) was recorded at OC (Figure 16b).
Family Acartiidae
The genus were presented by three species under one genus. Acartia simplex were recorded during study from all studied stations. Density of the species was high at HS and OC as compare to the HBM and SBM. Highest density was reported in October from HS (1766.66 Ind-m-3) and OC (1633.33 Ind-m-3) in 5m waters (Figure 17). A. amboinensis was recorded from all stations. The highest density was observed at OC during June in surface waters (1866.666 Ind-m-3) and at HS (2433.33 Ind-m-3) during August in 5m waters (Figure 17). A. Ohatsukai
Family Tortanidae
Only one species Tortanus barbatus was represented in the family Tortanidae. T. barbatus recorded with its highest density in surface waters at OC during August (666.66 Ind-m-3) and in October at HS (1133.33 Ind-m-3) in 5m waters (Figure 18).
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Figure 14. Annual vertical distribution and mean abundance (Ind. m-3) of the 3 species of family Temoridae at four stations in surface and 5m depth.
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Figure 15. Annual vertical distribution and mean abundance (Ind. m-3) of the species of family Candaciidae at all stations in surface and 5m depth.
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Figure 16a. Annual vertical distribution and mean abundance (Ind. m-3) of the 3 species of the genus Calanopia family Pontellidae at all stations in surface and 5m depth.
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Figure 16b. Annual vertical distribution and mean abundance of the species of family Pontellidae at all stations in surface and 5m (Ind. m-3) depth.
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Figure 17. Annual vertical distribution and mean abundance (Ind. m-3) of the species of the genus Acartia of family Acartiidae at all four stations in surface and 5m depth.
Figure 18. Annual vertical distribution and mean abundance (Ind. m-3) of Tortanus barbatus of family Tortanidae in surface and 5m depth at all four stations.
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3.1.2. DENSITY OF THE CYCLOPOID COPEPODS AT FOUR STATIONS
In present study order Cyclopoida was represented by 17 species in 4 families. The order was reported from all four stations.
Family Oithonidae
This family was represented by eight species e occupied by eight species. The species were recorded from all stations and shows fluctuation in abundance between stations (Figure 19a, 19b). Oithona rigida and O. brevicornis showed almost similar patterns of abundance during this study and were frequently recorded from all four stations. Oithona rigida and O. brevicornis were high at SBM (5966.66 Ind.m-3 and 3800 Ind.m-3respectively) in surafce waters. Whereas, in deeper waters the high density were observed at OC and HS during May. The decline in density was recorded from June to September 13 (Figure 19a). In surafce waters O. Pseudofrigida showed high density in March (300 Ind.m-3) and May (366.66 Ind.m-3) at HS and OC respectively. The high abundance of O. Pseudofrigida were recorded at HBM (433 Ind.m-3) during March. O. similis was high in abundance at OC during May (333.33 Ind.m-3) in surafce waters and during September 12 in deeper waters (200 Ind.m-3). O. Pseudofrigida and O. similis both species showed same decline in density from June to September. Similar to O. rigida and O. brevicornis (Figure 19a). O. linearis was recorded from all stations but with low abundance. The highest density of O. linearis was recorded from 5m waters at OC and SBM (166.66 Ind.m-3 during February and April respectively.
O. plumifera was abundant during December, January and March. The highest density was observed during December in surface waters at SBM (833.33 Ind.m-3) while in deeper waters the highest peak was recorded at HS and OC (Figure 19b). O occulata and O. attenuata were abundantly found at all four stations. High abundance of both species from all stations were recorded in May. Decline in abundance were recorded in June (Figure 19b). The highest peak of O occulata was recorded at SBM (1833.33 Ind.m-3) in May from
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surface waters. The density O. attenuata was recorded high in May at HBM and SBM (733.33 Ind.m-3) (Figure 19b).
Family Oncaeidae
The family Oncaeidae was represented by only one genus Oncaea, Three species of the genus were identified in present study. O. venusta showed its high abundance at HS during September in 5m waters (600 Ind.m-3). Oncaea conifera was noted frequently at all stations as compare to O. venusta and O. media. The peak density of the O. conifera was recorded at HBM and SBM during March. O. media was high during Decemeber at OC in both surface and 5m waters. The species was also abundant at HBM in December and March (Figure 20)
Family Sapphirinidae
Two genus Sapphirina and Copilia were identified in family Sapphirinidae. This family is the least abundant family in present study. Sapphirina auronitens was reported during April and August at OC and HS in surface waters. The high abundance of S. auronitens was noted at HBM during September 12 and October. At 5m depth Copilia vitrea and C. mirabilis was also less abundant. C. vitrea was recorded at HS and HBM only the highest density of C. mirabilis was recorded at OC in April (in surface waters) and October (in 5m waters) and this species was less abundant at HBM, SBM and HS (Figure 21).
Family Corycaeidae
Three species were identified in genus Coryaceaus. C. flaccus was the most abundant specie as compare to the other two (Figure 22). C. flaccus showed the highest density at HBM during March in 5m waters (2833.3 Ind.m-3). Other species was also reported to be high at HBM. C. flaccus and C. dahli showed almost same pattern of distribution. Both species were high at HBM in surface waters during April and March in both surface and 5m waters. The genus was not specific to habitat and abundantly found at all stations (Figure 22).
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Figure 19a. Annual mean abundance (Ind. m-3) and vertical distribution of the genus Oithona of family Oithonidae (order: cyclopoida) in surface and 5m depth at all stations.
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Figure 19b. Annual mean abundance (Ind. m-3) and vertical distribution of the genus Oithona of family Oithonidae (order: cyclopoida) in surface and 5m depth at all stations.
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Figure 20. Annual mean abundance (Ind. m-3) and vertical distribution of the genus Oncaea of the family Oncaeidae (order: cyclopoida) in surface and 5m depth at all stations.
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Figure 21. Annual mean abundance (Ind. m-3) and vertical distribution of the family Sapphirinidae (order: cyclopoida) in surface and 5m depth at all stations.
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Figure 22. Annual mean abundance (Ind. m-3) and vertical distribution of the order Corycaeidae in surface and 5m depth at all stations.
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3.1.3. DENSITY OF THE HARPACTICOID COPEPODS AT FOUR STATIONS
In the present study three families of harpacticoids was recorded with single representatives.
Family Ectinosomatidae
The family was noted with single genus and species. Microsetella norvegica was highly abundant at HS and OC as compare to HBM and SBM. During September and October the species was high at OC. Whereas in March the species was abundant in 5m waters at HS (700 Ind.m-3). This Species was completely absent during June to September 13 (Figure 23).
Family Euterpinidae
Euterpinidae was represented by single species Euterpina acutifrons. This Species was recorded throughout the year from September 12 to September 13 except from June. The high densities of E. acutifrons was recorded at OC throughout the year. Peak of abundance was recorded during August in surface waters (1800 Ind.m-3) and during October waters (2100 Ind. m-3) (Figure 23).
Family Clytemnestridae
Clytemnestra scutellata was the single species recorded in family Clytemnestridae. In surface waters this species was not recorded at OC whereas at 5m waters the species was repcorded at all stations. The highest abundance was noted in September at HBM in surface waters (466.6 Ind.m-3) and in 5m at HS in March (500 Ind.m-3) at 5m (Figure 23).
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Figure 23. Annual mean abundance (Ind. m-3) and vertical distribution of the order Harpacticoida in surface and 5m depth at all stations.
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3.1.4. DENSITY OF THE MONSTRILLOIDS COPEPODS AT FOUR STATIONS
Order Monstrilloida was represented by only one family Monstrillidae with a single genus Cymbasoma. Two species of the genus C. longispinosum and C. williamsoni were identified during this study.
Family Monstrilloida
The high abundance of C. longispinosum was recorded at OC in October and November and was completely absent during March to June. C. williamsoni was high at HBM in surface waters (233.3 Ind.m-3) in October and at OC (633 Ind.m-3) during September 12 at 5m waters (Figure 24).
Among stations most of the species was frequently observed with 100 % frequency of occurrence (Table 3). Eucalanus bungii, Eucheata marina and Pontella securifer was totally absent from station HS. Whereas at OC Candacia discaudata, Acartia ohatsukai and Copilia vitrea was totally absent. 10 species which included Rhincalanus Sp., Clausocalanus. Minor, C. karachiensis, C. chierchiae, C. alocki, Candacia sp., Pontella securifer and Calanopia genus were absent at HBM. 16 species were completely absent from SBM (Table 3). From mangrove stations less diversity was recorded as compare to other two stations. The relative abundance of copeods species at all four station was noted (Table 3). Temora turbinata showed the highest relative frequency followed by Oithona rigida and Pseudodiaptomus serricaudatus (Table 3).
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Figure 24. Annual mean abundance (Ind. m-3) and vertical distribution of the order Monstilloida in surface and 5m depth at all stations.
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3.2. VARIATION IN TOTAL COPRPODS BETWEEN STATIONS
The Total of copepods group abundance showed monthly fluctuation. From HS and OC the highest mean density of copepods were recorded during October 39733 Ind.m-3and 29900 Ind.m-3 respectively. From estuarine stations the High mean density was recorded at HBM during March (17150 Ind.m-3) and from SBM the peak mean abundance was recorded during May (32366 Ind.m-3). HS was reported with highest copepods count which was followed by SBM, OC and HBM (Figure 25).
Figure 25. Mean density of copepods taxa in surface and 5m depth (Ind.m-3) at all stations from September 12 to September 13.
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Table 3. Total abundance of species Ind.m-3 at all stations with their occurrence frequency (OF %) and relative frequency (RA %).
Taxa HS OC HBM SBM OF % RF% Taxa HS OC HBM SBM OF % RF % Undinula vulgaris 866.667 1566.67 33.3333 0 75 0.32 Candacia discaudata 700 0 433.333 533.333 75 0.22 Cathocalanus pauper 3866.67 1433.33 700 1100 100 0.94 Candacia sp. 466.667 2300 0 0 50 0.36 Acrocalanus longicornis 8933.33 14233.3 8966.67 7800 100 5.29 Calanopia elliptica 5966.67 300 0 0 50 0.83 A.gracilis 12500 3166.67 2000 100 100 2.35 C. minor 433.333 433.333 0 0 50 0.11 A. monachus 10600 5583.33 200 3500 100 2.63 Calanopia Sp 98 3766.67 1533.33 0 0 50 0.7 A. gibber 5200 1933.33 115.47 3500 100 1.42 Labidocera acuta 100 433.333 833.333 66.6667 100 0.19 Acrocalanus Specie 1 4633.33 2766.67 2466.67 2700 100 1.66 L. pectinata 766.667 1400 166.667 700 100 0.4 Acrocalanus Specie 2 2766.67 1733.33 1000 1833.33 100 0.97 Pontella securifer 0 2366.67 0 133.333 50 0.33 Bestiolina arabica 4366.67 1800 1166.67 1933.33 100 1.22 Acartia simplex 6033.33 6233.33 2366.67 1233.33 100 2.1 B. similis 17300 2000 2800 1466.67 100 3.12 A. amboinensis 3466.67 5700 3466.67 2333.33 100 1.98 Paracalanus parvus 2300 2633.33 733.333 1066.67 100 0.89 A. ohatsukai 66.6667 0 66.6667 100 75 0.03 Eucalanus bungii 0 1100 766.667 0 50 0.24 T. barbatu 4200 1533.33 533.333 466.667 100 0.89 Subeucalanus crassus 600 1066.67 233.333 150 100 0.27 Oithona rigida 13766.7 12833.3 12133.3 27800 100 8.82 S. subcrassus 3066.67 2966.67 3200 1733.33 100 1.45 O. brevicornis 5200 3966.67 3033.33 4966.67 100 2.27 S. pileatus 2500 2166.67 400 2333.33 100 0.98 O. pseudofrigida 900 1300 966.667 233.333 100 0.45 S. subtenuis 66.6667 3533.33 1100 133.333 100 0.64 O. similis 400 1200 266.667 66.6667 100 0.25 Rhincalanus Sp. 400 1366.67 0 0 50 0.23 O. linearis 433.333 400 33.3333 466.667 100 0.17 Clausocalanus. minor 1766.67 566.667 0 966.667 75 0.43 O. plumifera 3800 3300 3033.33 4700.58 100 1.96 C. furcatus 600 1583.33 766.667 0 75 0.39 O. occulata 2800 1966.67 2266.67 2700 100 1.29 Eucheata marina 0 900 933.333 0 50 0.24 O. attenuata 1600 1366.67 1766.67 1800 100 0.86 Centropages orsinii 4966.67 2900 1366.67 1466.67 100 1.41 Ooncaea venusta 1700 1333.33 2433.33 233.333 100 0.75 C. dorsispinatus 2666.67 2000 666.667 600 100 0.78 O. conifera 4566.67 7133.33 8100 6433.33 100 3.47 C. karachiensis 533.333 3566.67 0 0 50 0.54 O. media 2366.67 2800 2766.67 1100 100 1.19 C. tenuiremis 9400 6766.67 4433.33 2733.33 100 3.09 sapphirina auronitens 100 133.333 500 0 75 0.09 C. furcatus 1433.33 5400 2166.67 833.333 100 1.3 Copilia vitrea 466.667 0 166.667 0 50 0.08 C. hamatus 500 100 533.333 100 100 0.16 C. mirabilis 33.3333 400 66.6667 166.667 100 0.08 C. chierchiae 566.667 266.667 0 0 50 0.11 Corycaeus crassiusculus 6666.67 5733.33 6700 5600 100 3.27 C. alocki 433.333 233.333 0 133.333 75 0.1 C. flaccus 4466.67 3866.67 6800 3866.67 100 2.51 Pseudodiaptomus serricaudatus 15233.3 19266.7 7800 4333.33 100 6.18 C. dahli 2566.67 2733.33 2533.33 1633.33 100 1.25 P. arabicus 4433.33 1866.67 2633.33 0 75 1.18 M. norvegica 1233.33 2366.67 1500 633.333 100 0.76 P. aurivilli 1666.67 500 33.3333 0 75 0.29 E. acutifrons 9633.33 15833.3 4400 8133.33 100 5.03 Temora turbinata 32733.3 43633.3 19033.3 11433.3 100 14.16 C. scutellata 833.333 500 1200 666.667 100 0.42 T. discaudata 1533.33 1533.33 366.667 700 100 0.54 C. longisinosum 866.667 2833.33 266.667 333.333 100 0.57 T. stylifera 1233.33 466.667 266.667 0 75 0.26 C. williamsoni 433.333 1166.67 233.333 100 100 0.25 99
3.3. SEASONAL VARIATION IN ABUNDANCE OF COPEPODS
Total density of order Calanoida, Harpaticoida and Cyclopoida with respect to monsoon season was given in figure 26. The highest density of total copepods were recorded in SWM season at all stations. All of the three orders showed high density during SWM season. At HS and OC the copepods were less abundant in PRE monsoon season. At HBM and SBM least density was recorded during POM. Similar pattern of seasonal variation was recorded within the mangrove and non-mangrove stations (Figure 26).
The species also show seasonal variation in abundance within the genus seasonal variation was observed among species (Table 4a, b). Among Calanoida total species density of family Calanidae, Centropagidae, Acartiidae and Toranidae showed high abundance in SWM seasons whereas, Rhincalanidae, Clausocalanidae and Temoridae was recorded with high density in NEM. Euchaetidae, Pseudodiaptomidae and Pontellidae showed high desnsity during POM (Table 4a). Family Euchaetidae was the least abundant calanoid family which recorded only in POM and NEM seasons.
Families of order cyclopoida showed different seasonal pattern of abundance. The family Oithonidae family was present with high density in SWM. Oncaeidae was recorded high during NEM whereas Sapphirinidae was recorded with same density during PRE ans NEM monsoon season. The most abundant family Corycaeidae was recorded high in PRE monsoon (Table 4b).
Three families of order harpacticoida Euterpinidae, Clytemnestridae and Monstrillidae showed high density during SWM, PRE and NEM monsoon respectively (Table 4b).
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Figure 26. Seasonal distribution and density (Ind.m-3) of three orders and total copepods during monsoon seasons.
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Table 4a. Species wise seasonal fluctuation of order calanoida during PRE (pre- monsoon), SWM (southwest monsoon), POM (post monsoon) and NEM (northeast monsoon). First records*
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Table 4a Continue …..
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Table 4b. Species wise seasonal fluctuation of order cyclopoida and harpacticoida during
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all four seasons. First records* 3.4. STATISTICAL ANALYSIS
Genus (8) association were analyzed between Stations HS and OC, HBM and SBM. Acrocalanus genus showed significant relation at HBM vs SBM (R2=55.9, P=0.08) and OC versus mangrove (R2=89.4,P=0.004). (Table 5).
Sigificant relation of Centropages density was recorded beween HS and mangrove (R2=87.1, P=0.001).
Pseudodiaptomus showed strong significant relation between HS and mangrove (R2=100, P=0.007). Whereas little significant relation was observed between mangrove stations (R2=89.1, P=0.2).
Regression analysis reveals significant relation of Temora density between HS and OC (R2=100, P=0.009). Oithona showed significant relation between all stations. Corycaeus showed significant relation between HS and OC (R2=99, P=0.062). Harpacticoids was significantly present between all stations (Table 5).
Table 5. Linear regression analysis and one-way ANOVA (P < 0.05) between stations for copepods species.
HS vs OC HBM vs SBM HS vs Mangrove OC vs mangrove Genus R-sq F P R-sq F P R-sq F P R-sq F P Acrocalanus 14.6 0.68 0.455 55.9 5.07 0.087* 1.2 0.05 0.836 89.4 33.76 0.004* Centropages 48.7 5.71 0.054* 88.6 46.76 0 87.1 40.66 0.001* 68.7 13.16 0.011* Pseudodiaptomus 98.3 59.59 0.082* 89.2 8.25 0.213 100 7749.73 0.007* 98 50.22 0.089* Temora 100 5587.64 0.009* 99.8 399.1 0.032* 100 4468.96 0.01* 100 400250 0.001* Acartia 87.2 6.81 0.233 96.3 26.35 0.122 44.5 0.8 0.535 79.1 3.78 0.302 Oithona 98.3 341.25 0 98.6 414.73 0 97 192.11 0 98.8 493.4 0 Corycaeus 99 103.49 0.062* 79.4 3.85 0.3 86.6 6.46 0.239 79.3 3.82 0.301 Hepacticoids sp. 99.5 194.75 0.046* 99.2 126.05 0.057* 100 2973.25 0.012* 99.2 123.14 0.057*
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Dendrogam of cluste analysis at HS was composed of the 3 main cluster. Cluster identified the monthly and seasonal variation in total copepods (Figure 27). June stands separately in cluster because of less abundance. Copepods was clustered during SWM months except June. NEM monsoon month grouped in singal cluster. (Figure 27).
At OC dendrogram of cluster analysis showed two main clusters. June stands separate from other months. Similarity among seasonal months did not show the significant clusters (Figure 27).
At HBM Bray-Curtis similarity was presented by 2 main clusters June and August was separated from other months. Seasonal variability was observed during all seasons. SWM was clustered together except May and September 12. NEM moths was clustered together except January (Figure 28).
At SBM cluter analysis showed less similarity between months. June and August are separated with the unique abundance of copepods. Similarity among the seasonal months varied. No seasonal similarity was observed (Figure 28).
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OC Dec Monsoon Nov SWM POM Oct NEM S12 PRE May Feb Apr Jan Mar S13 Aug Jul Jun
0 20 40 60 80 100 Similarity
Figure 27. Cluster analysis based on Bray-Curtis similarity matrix calculated through monthly and seasonal density of copepods at two non-mangrove sites (HS and OC).
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HBM May Monsoon Oct SWM S12 POM Apr NEM Jan PRE Mar Feb Dec Nov S13 Jul Jun Aug
0 20 40 60 80 100 Similarity
SBM Dec Monsoon Nov SWM POM Apr NEM May PRE S12 Mar Jan Feb Aug S13 Jul Oct Jun
0 20 40 60 80 100 Similarity
Figure 28. Cluster analysis based on Bray-Curtis similarity matrix calculated through monthly and seasonal density of copepods at two mangrove sites (HBM and SBM).
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4. DISSCUSION
4.1. COPEPODS COMMUNITY PATTERN During this study copepods was the major group among rest of the mesozooplankton. Their dominancy has been noted in previous finding from all over the world. (Calbet et al., 2001; Dur et al., 2003; Fernandez et al., 2003; López-Ibarra and Palomares-García 2006; Fernandes and Ramaiah, 2014; Abbasi et al., 2016). The dominancy of copepods (66%) as compare to MZ has been reported earilier from Pakistani waters (Naz et al., 2014). Among copepods the density of calanoids were highest at all stations as compare to other three orders. The highest calanoid occurrence has been reported from the other parts of the Oceans as well as from estuarine ecosystems (Haq et al., 1973; Madhupratap and Haridas 1986; Kibirige and Perissinotto, 2003; Yamaguchi et al., 2004; Champalbert, et al., 2005; Leandro et al., 2007).
The current study added the important information in the taxonomic account from Pakistani waters. In the present study, 23 new species of copepods has been reported for the first time from Pakistani waters. Very little attention was given in the past decades to the identification of zooplanktons species specially copepods in our area. Although many of these species has been reported earlier from neighbouring countries such as India, Kuwait and Omani (Kasturirangan, 1963; Al-Yamani et al., 201). Acrocalanus gibber, Paracalanus parvus, Eucalanus bungii, Centropages chierchiae, C. alocki, C. calanius, Pseudodiaptomus arabicua, P. aurivilli, Temora stylifera, candacia discaudata, Acartia simplex, and A. ohasukai are addition in the information of calanoid copepods in Pakistani waters. Some of the Oceanic species such as A. ohatsukai which is recorded first time from study area was not present abundantly and might be introduced to the inshore waters. Among cyclopoids, first records of Oithona species recently have been given by Ara et al., 2017 (present study). Only a single species Oithona plumifera was reported earlier from Pakistan. These small copeods of the Oceans (Neumann-Leitão et al. 2008) require precise mesh size net for sampling to reduce sampling errors. Corycaeus dahli and C. asciaticus were also reported first time from our area. The study indicates that calanoid family Temoridae, Paracalanidae and Pseudodiaptomidae were the most abundant copepods in our study area and T.
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turbinata was the most abundant copepods species. Its occurrence and wide distribution in Indian, Atlantic and Pacific Ocean has been reported from other parts of the world (Fleminger, 1975; Bradford-Grieve et al., 1999). The T. turbinata was less abundant during summer. Similar pattern of distribution was recorded from Mexico and Brazil (Suárez-Morales and Gasca, 1996; Ara, 2002). The family Paraclanidae was represented by three genus Acrocalanus, Bestiolina and Paracalanus. Acrocalanus longicornis was widely distributed at all stations as compare to other 5 species of the genus. From Pakistani waters A. longicornis have been noted to be found abundantly (Haq et al., 1973; Naz et al., 2012). Family Pseudodiaptomidae was represented by three species and Psudodiaptomus serricaudatus occupy the major occurrence in the family.
Cyclopoid copepods were represented by three dominant families; Corycaeidae, Oithonidae and Oncaeidae which occupied 37%, 31% and 28% respectively. Abundance and frequent occurrence of Corycaeidae has reported in earlier reports from upper Oceanic layer (Boxshall 1977). Species in the genus Oithona during this study showed wide abundance at all selected stations. Oithona and Oncaea exhibit wide range of distribution worldwide and these small copeods are highly sensitive to the mesh size (Evans, 1973; Paffenhöfer 1993; Paffenhofer, 1998). Family Euterpinidae represented by only one species which build 76% of the total harpacticoids during this study. From other parts of the world Euterpina acutifrons was reported to be frequently occur throughout the year (Ara, 2001).
4.2. ANNUAL VARIATION IN COPEPODS SPECIES ABUNDANCE
Different species show different spatial and temporal variation in abundance which explains the fluctuation in the fitness of the ecosystem. Undinula vulgaris was reported to be found only in inshore surface waters. Although it has been frequently reported in inshore water as compare to the Oceanic environment (Woodd-Walker, 2001). High density of U. vulgaris was noticed during October. Similar result of high density was given for Manora channel back in 1975 (Khan, 1979). The high density of Cathocalanus pauper was recorded during October (just after summer). The species 110
was reported to be found abundantly during summer and spring months and less in winter (Hedayati et al., 2017). Within the genus different spatial variation in species was recorded. A. longocronis was widely present but the highest density was recorded of .A gracilis as compare to A. longicornis. The peak was reported in October same result from Taiwan was given in October 2007 the species was dominant with 3.9 % relative abundance among the five dominant species (Chien, 2003; Chou et al., 2012). In November Paracalanus parvus was the most abundant species. In previous study the high density of P. parvus was reported in June, 1975 (Khan, 1979).
The comparison of abundance pattern of P. parvus with previous study indicates dissimilar abundance pattern. High salinities favors high population of Bestiolina sp. This categorize the Bestiolina as euryhaline species, reported before from Indian waters (Goswami 1982; Dalal and Goswami 2001). Eucalanus bungii was abundant at OC which receives the open ocean effect. Earlier study about the life cycle of the species reveals summer as a peak season for the abundance from Pacific waters (Shoden et al., 2005). Subeucalanus species was observed throughout the year and was reported as epiplanktonic species from Pakistani waters (Haq et al., 1973). Spatial and temporal variation of eight species of the genus Centropages was reported in this study. C. tenuremis, C. orsinii, C. dorsispinatus and C. furcatus was reported to be the abundant species during study. Khan, 1973, reported high density of C. dorsispinatus and C. furcatus in October, whereas, the current study showed high density of these species during September and November. Three species Centropages hamatus, C. alocki, C. calanius are reported for the first time from Pakistani waters. These species was reported from Indian waters (Kasturirangan, 1963). Species of Pseudodiaptomus was found high during low temperature months. P. arabicus and P. aurivilli are reported for the first time from Pakistan waters and their high abundance was noted during September. A study from south-west part of Mediterranean Sea reported the high density of P. arabicus during September (Ounissi, 2016). Three species of Temora: T. turbinata, T. discaudata, T. stylifera was present with high abundance. Haq, 1973 also reported it as a bulky species in epiplanktonic copepods. A study from Taiwan presented the 29.3% relative abundance of T. turbinata which was the highest as compare to others (Chou et al., 2012). We found similar pattern of T. discaudata abundance as described in earlier study. The highest density was reported for T. discaudata in October (Khan, 1979). Candacia discaudata, A. ohatsukai are 111
reported for the first time from Pakistani waters and their abundance was only noted 2 to 3 times in whole study period. Acartia simplex, was found throughout the study period. Tortanus barbatus was found first time from Pakistani waters. Its high density was noted during October. From Kenya earlier study showed the dense population of species from December to March (Revis, 1988). Their abundance and occurrence has also reported from Indian waters during 2010 and 2011(Thirunavukkarasu et al., 2013). Small copepods includes genus Oithona, Oncaea and Corycaeus (Calbet et al., 2001). Corycaeus was the dominant genus which was frequently recorded from here and other parts of the world Oceans (Razouls et al., 2005-2016). Corycaeus was reported high during warm season. Occurrence in warm water was also reported from Mediterranean Sea and Pacific Ocean (Vidjak and Bojanic, 2009; Batten and Walne, 2011). C. flaccus was the dominant species among three species of the genus in current study. From Pakistani waters C. flaccus was reported as the abundant species among epiplanktonic copepods in 1973 (Haq, 1973). The same pattern has reported in this research. Abundance of eight species of Oithona was noted during study period. Seven was reported for the first time from Pakistan coast. Ecological importance of Oithona and their role has been studied from various parts of the world. Their bulk of abundance and distribution have reported from various habitats of the marine environment (Rezai et al., 2004; Satapoomin et al., 2004;Castellani et al., 2007; Robin et al., 2009) but the genus was left inattentive in past from Pakistan. O. rigida was the dominant species of genus but unfortunately was not reported before from the study area. Distribution of O. rigida O. brevicornis and O. similis showed the similar pattern of abundance as reported from Indian waters in earlier study (Godhantaraman, 1994). The Oithona showed its high density in May. The same has been reported from Indian waters where these species was high during April and May (Godhantaraman, 1994). O. plumifera was reported from all station with high density in December. Similar results were presented from Mediterranean Sea where O. plumifera have been reported during winter (Zakaria et al., 2016). Genus Oncaea was represented by the high abundance of O. conifera. The species was noted to be absent during warm season. O. conifera was reported to be abundantly found during winter in inshore waters (Escribano and Hidalgo, 2000). Harpacticoid copepods were gain less previously privilege in past as they were considered as of no importance within the trophic link (Heip and smol, 1976). Later the work on this order reveals its 112
importance in the food web and in fisheries economy (Huys et al., 1996; Buffan- Dubau and Carman, 2000). Euterpina acutifrons was recorded abundantly as compare to other two species of the harpacticoid copepods. A study from western Portugal reported the dominancy of E. acutifrons as compare to other harpactiocid (Goncalves et al., 2010).
4.3. SEASONAL EFFECTS ON COPEPODS
Copepods is a diverse group among mesozooplanktons. The seasonal distribution of copepods were recorded to see the seasonality effect on the distribution of zooplanktons. Within copepods some species receive seasonal effect and some of the species does not respond to the seasonal change (Calbelt et al., 2001; Cornils et al., 2010). SWM season is recorded to be rich in biodiversity which was followed by NEM. A study from Manora channel reveals SWM as the high abundance season (Khan, 1979). From Arabian Sea the copepods were reported with high density during NEM seasons (Kidwai and Amjad, 2000). A study from Bangladesh has reported monsoon as zooplankton peak season (Zafar, 2007). Monsoon winds enable the mixing of nutrients which support the zooplankton growth which eventually increase the zooplankton numbers (Marra and Barber, 2005). In marine environment, the high abundance of calanoid, and cyclopid which were followed by harpacticoid copepods is generally accepted (Calbelt, 2001: Thirunavukkarasu, 2013, Abbasi et al., 2017). In this study the same order of abundance was obtained except during PRE monsoon where cyclopoid was abundant as compare to calanoid at all stations. PRE monsoon is dry and hot season which favours the cyclopoid whereas the winter months are abundant months for calanoid (Calbelt et al., 2001). During this study the peak abundance during October at HS was noted which might be due to the availability of food. This station receives Layari River discharge which indirectly favours the suitable environment for the development of tolerant species. From Korean waters study shows the high copepods abundance during October (Vargas et al., 2002). The decrease in copepods abundance in summer washas been reported from other parts of the world (Rawlinson et al., 2005; Yaqoob et al., 2013).which is in contrast to he present study in which high density of copepods was recorded in SWM(summer monsoon ) season. 113
5. CONCLUSION
Copepods community structure, their seasonal and annual pattern of distribution was estimated in this chapter. A total of 69 species of copepods were identified. 4 orders were comprised of 21 families. 47 species were in order calanoida, 17 species were identified in order cyclopoida and 3 species were the representative of order harpacticoida. And a singal species was reported in order Monstrilloida. Order calanoida was reported as the dominant order and Temora turbinata was the most abundant species in inshores waters of Manora Channel. Annual abundance was measured high in October. Whereas the SWM season support high zooplankton count. In this study 23 first records were identified from Pakistani waters.
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EEFECTS OF ENERGY FLUX ON THE CHAPTER # 4 DISTRIBUION OF ZOOPLANKON IN MANGROVE FORESTS ALONG THE COAST OF KARACHI
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ABSRACT
Effect of mangrove energy flux on zooplankton community was accessed by the phytoplankton production and its trophic partaking to primary consumers which are zooplanktons. Major nutrients concentrations were determined to study the effects of nutrients on primary production. HS, a polluted station, was rich in NH4 and NO3 concentrations as compare to OC. At HBM substantial relation of NH4 was recorded with the phytoplankton biomass. Although nutrients provide energy for the growth of phytoplankton, other physical variables are also responsible for their growth such as temperature, DO and turbidity. Annual findings illustrate that the omnivore zooplankton were the major consumers in mangrove forest among the functional feeding groups of zooplankton. 56% and 59 % space was occupied by the Omnivore group at HBM and SBM respectively. Only 2-4% of the total zooplanktons were detritivore zooplankton.
The tidal cycle was covered at HBM to study the mangrove influence. Overall nutrient concentration was high at MT and low at HT indicating outward flux of nutrients from mangroves. The same pattern was noted for phytoplankton biomass. Zooplankton density was high at HT and LTn as during night the zooplankton moves towards the surface. The phenomena of Dial-Vertical Migration was noted during tidal cycle as indicated through the high density of zooplankton during night sampling. The omnivore zooplankton were high during HT and MT. Inverted energy pyramids was formed at LTs where the detritivore zooplankton dominated the other groups. The out-welling of detritus from mangroves might be the possible cause of high abundance of detritivores at LTs.
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1. INTRODUCTION
Mangrove ecosystem stands with its special position between the Marine ecosystem and its surroundings. These forest make the strong association between land and ocean. They protect the biodiversity of the ecosystem by sheltering the biota of the region from hazards (Melo et al., 2010). They offer habitat for a wide variety of single cell animal like bacteria to the large mammals (FAO, 2004). Deforestation of Mangrove forest has been increased during the last decades which may be the cause of Coastal developments of the area (Spalding et al., 2010). Worldwide distribution, mangroves forests occupy 15 mil-hectares and dominates in the tropical and subtropical shoreline (FAO, 2004). 30 to 50% global mangrove deforestation have been occurred because of the coastal development during the last 50 years (Valiela, et al., 2001; Duke et al., 2007; Spalding, et al., 2010). Profligate disappearance of mangrove forests reported to alter the hydrobiology of the tropical mangroves and subtropical wetlands which consequently effect the adjacent ecosystem like earthen cycles, food web dynamics, small to bigger community structure and nutrient flow (Winemiller and Jepsen, 1998; William and Trexler, 2006; Zedler and Kercher, 2005; Douglas et al., 2005; Govender, et al., 2007). Excessive production, energy and nutrient flux and carbon loading mainly associated with mangroves in marine ecosystem. (Duarte and Cebrian 1996). Mangrove forest exhibit inimitable energy flux because of their distribution and evergreen growth pattern (Barr et al., 2010). Strong relationship in coastal ecosystem occurs between sea surface level and nutrient energy stream (Hoguane et al., 1999). Litter fall proved to be the continuous source of the mangrove nutrients in all seasons (Clough et al., 2000).
Mangrove ecosystem is highly productive ecosystem in the world (Alongi 2009) and they act as the major sink for the Carbon (Twilley et al., 1992). Just because of this the mangrove ecosystem is the carbon enrich ecosystem (Murdiyarso et al., 2015). Salinity, tidal currents and nutrients are the major components of environmental fluctuation in estuarine ecosystem (Allen et al., 2008, Costa et al., 2013). Low tidal currents facilitate the sinking nutrients such as phosphate and nitrate sink down to the bottom whereas high tide facilitate the mixing of nutrients than results in the virtuous nutrient exchange between mangrove and adjacent ecosystems (Lara and Dittmar,
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1999). Nutrients are the component which are the key factor for the mangrove growth and healthy environment. N and P found naturally in water their most common forms are nitrate and phosphate. Nitrate, ammonium and phosphate are the nutrients which are the key for the water quality assessment. Tidal induced changes and other climatic factors contribute in the energy flux within mangrove areas which is quite difficult to measures. In ecosystem, flow of nutrients can be possibly estimated via community structure which comprised of autotrophs and heterotrophs. Autotrophs makes complex organic compound which are transformed and decomposed by heterotrophs eventually transferred back to the ecosystem. (Falkowski et al., 2008). These primary consumers has not only been used as a food source for fishes during their early life stages in mangrove waters but also act as the indicator of the healthy environment of ecosystem (Day et al., 1989). Mangroves are supposed to play the major role in transferring energy from primary level of biological activity to the upper trophic levels (Nagelkerken, 2009; McLusky and Elliott, 2004). Mangrove habitat is rich in detritus derived from the litter production and decomposition of dead animals and other organic substances (Bouillon and Connolly, 2009). In mangroves Autotrophic biomass becomes high upon the availability of the nutrients from mangroves litter production (Singh et al., 2005).
In trophic status mesoszooplankton have significant position and a major link in food web. The fisheries potential is strongly correlated to the healthy environment of the Ocean which biologicaly cause by the zooplankton population. In mangrove forests the abundance distribution and variation in their population caused by different factors which includes biological (concentration of phytoplankton biomass, predation and cannibalism among the copepods), physical and tidal variations. Planktons have been prevailing component in the marine trophic interactions but the copepods have substantial importance for the fish larvae within the marine food web (Farhadian et al., 2009; Santhanam et al., 1975). Each taxa in MZ community have its specific status in food web (Bernadette et al., 2017). Feeding links, feeding dependency and predation prey relation all collectively effect the ecology of an ecosystem. Herbivores autotrophs are the primary consumers which transfer energy to the carnivore heterotrophs hence secondary consumers. This flow of energy from lower to upper trophic stage loose some energy in the form of faecal pallets and waste products.
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In mangrove forests phytoplankton and zooplankton communities get durable influence of tidal cycles. The tides produces mechanical energy in terms of water inflow and outflow in mangroves. This energy not only effect the nutrient distribution in the water column and also the biota of the system. High and low tides are responsible for the transportation of material from mangroves forest to the open ocean hence maintain the continuous flow of energy and the community pattern changes vertically and horizantly with the tidal currents (Blauw, et al., 2012). Spatiotemporal variation of zooplankton and phytoplankton biomass determines the energy flow within their community and system (Halliday, 2001)
Sandspit back waters mangrove forest influence the nutrient output in Manora channel and also effect the phytoplankton production of the area. (Siddiqui and Shafique 2000). They ultimately influence the distribution of the resident zooplankton community. From Pakistani waters works on nutrient and Chl a determination in mangrove forest has been reported by (Shoaib et al., 2017; Farooq and Siddiqui, 2010; Harrison et al., 1997). But the effect of mangrove energy flux on the resident communities of s has not been evaluated before the current study.
The aim of this study is to evaluate the nutrients and its relation to phytoplankton and zooplankton dynamics in mangroves. Tidal and annual variation in nutrient and its influence on zooplankton dynamics was measured and their role in trophic interaction was conducted.
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2. MATERIAL METHODS
2.1. COLLECTION SITES
The study site has discussed in 2nd chapter.
Go back to the chapter 2 (pg. 20-21)
2.1.1. COASTAL WATER STATIONS HS AND OC
The study station HS and OC have described in 2nd chapter. Go back to the chapter 2. (Pg. 220).
2.1.2. MANGROVE FOREST STATION HBM AND SBM
Two mangrove stations were selected to evaluate the effect of mangrove energy flux on zooplankton distribution. Station description has given in chapter 2. Go back to the chapter 2. (Pg. 23)
2.2. SAMPLING
Collection of waters samples were collected during HT throughout the year In addition to the yearly sampling, the tidal cycle was evaluated at Mangrove station (HBM) during June 2013. At HBM four tides in a day were covered to assess the nutrient fluctuation with respect to other biological parameters (Chl a and zooplankton abundance). The low tide (LT) was captured at -0.1m, high tide (HT) was taken at 3.2m tidal height , mid tide (MT) was taken at 1.5m and low tide after sunset (LTn) was captured at 1m height (Figure 1).
2.2.1. COLLECTION AND ANALYSIS OF ABIOTIC VARIABLES
Physico-chemical variables were analysed on boat which includes temperature, salinity, DO, transparency and TSS. Biotic variable includes the Chl a concentration. These variables were analysed by the method as described in previous chapter. The nutrient concentration were analysed as described below.
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Figure 1. Tidal chart showing tidal height variation and time during complete tidal cycle.
2.2.2. ANALYSIS OF NUTRIENTS
Water sampling for the analysis of nutrient contents was conducted on high tide preferably at morning from September 2012 to September 2013 at all stations SBM, HBM, HS and OC. In addition to this for the assessment of tidal induce changes in nutrient content of a specific site was estimated at HBM during MT, LT and LTn. Water samples were immediately filtered and stored in pre washed bottles in ice.
In laboratory the samples were treated with the APHA Standard methods for the analysis of Ammonia, Nitrate and Phosphate.
Ammonia was determined by indophenol blue method by APHA (APHA, 2005).
The chemicals reagents which was used for this method Phenol and alcohol reagent (95% ethyl alcohol), sodium nitopursside, trisodium citrate and sodium hydroxide reagent, sodium hypochlorite and oxidixing solution. Samples were calibrated via
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proper instruction and absorbance were taken at 630nm via UV-visible spectrophotometer.
Nitrate in samples was determined by the cadmium reduction method by Strickland and Parson. All chemical reagents were used to make the solution as per given (Strickland and Parson, 1972).
Acid washed cadmium-copper column was 30cm long. Fill the column with CuSO4 hydrate solution till the disappearance of blue colouration stir the cadmium column. The column should wash with diluted ammonium chloride. 1 ml of NH4Cl were added in 100 ml sample and mix the solution. From which 5ml of the solution were added to the column after that whole solution was passed through the column and collected the sample in flask. After reduction 1ml of sulanilamide added to the flask solution. 5 minutes required for reaction. 1ml of N-(1-Naphthyl)-ethylenediamine dihydrochloride was added to the flask solution and then at 543nm the absorbance of solution was measured. Before standardisation blank reagent absorbance was taken. The nitrate in mg/L was estimated against standard reading by plotting graph.
For the determination of phosphate Ascorbic acid method was used as described in APHA methods. In acidic medium ammonium molybdate and antimony potassium tartrate was reacted. In result of this reaction a complex form which is antimony- phospho-molybdate. This complex reduce to intense blue colour complex in the presence of Ascorbic acid. With the help of spectrophotometer the absorbance was recorded at 880nm. Which was further used in calibration and calculation for the concentration of phosphate.
2.2.3. COLLECTION AND ANALYSIS BIOLOGICAL PARAMETERS
During tidal and annual sampling the phytoplankton biomass (Chl a) was estimated by spectrophotometric method as described in ICES techniques (Harries et al., 2000). Detailed description is given in chapter 2 page 25.
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Zooplankton from all stations were collected in replicates in each site through zooplankton net with the mouth diameter 0.29m and 170 micron mesh size. Vertical sampling was carried out at up to 5m waters. Samples were removed from net to cleaned wide mouth plastic jars. The samples were preserved as described in previous chapter.The total number of zooplankton was estimated by using chamber plate method. For the tidal data of zooplankton at each tide the samples were collected and estimated up to the generic level. Zooplankton annual and tidal data was processed and analysed as described in ICES zooplankton manual (Harries et al., 2000).
2.2.2.3. FEEDING GUILDS
For the estimation of energy flow, the trophic interaction within zooplankton was estimated by using feeding guilds composition as previously described in different studies (William et al., 2012). Description of each feeding group is described later in this chapter. On the basis of zooplankton feeding behaviours four guilds were formed Carnivore, Herbivore, Omnivore and Detritivore. Carnivore guild include the coelenterate, ctenophore, lucifer, chaetognaths, other marine planktonic worms, fish eggs and larvae and polychaete worms. Herbivore guild consist of Salps and doliolids, appendicularian, crustacean larvae (nauplli and zoeal stages), cladocerans, echinoderm larvae, gastropods and bivalve. Omnivore guild comprise of copepods, mysids and ostracods. Nematodes was included in detritivore guild.
2.2.3.2 ESTIMATION OF ZOOPLANKTON BIOMASS
3 Zooplankton biomass (ZB) g/m were calculated by wet weight of s (ZW) before weighing, debris were removed from samples. ZB = ZW *VF
Where ZW = zooplankton wet weight VF = volume of water filtered.
2.3. STATISTICAL ANALYSIS
Regression analysis and ANOVA was performed to evaluate the significance among nutrient concentration and phytoplankton biomass. Tidal heights and its relation to other parameters were also analysed by ANOVA and regression analysis.
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3. RESULTS
3.1. ANNUAL NUTRIENT DISTRIBUTION
3.1.1. NUTRIENT FLUCTUATION AT HS AND OC
The concentration of ammonia showed summer and winter peaks. The highest concentration was observed in August (20.8 and 6.5mg/L respectively during August. January to May low values were obtained from these sites in July and May (Figure 2)
Nitrate in HS and OC waters was recorded. At HS high concentration was found during June (32.1mg/L) and at OC during December (14.3mg/L). From mangrove forest both stations expressed contrasting results. Phosphate concentration was also noted. Fluctuation among both stations HS and OC was recorded in October (Figure 2).
3.1.2. NUTRIENT FLUCTUATION AT HBM AND SBM
The highest peak of Ammonia concentration was noted during November and than in August at both HBM and SBM (Figure 3). At HBM the highest value of nitrate was recorded during October and lowest during July. Whereas during July the peak was recorded at HBM 17.8 mg/L (Figure 3).
During January, April and June the phosphate was high at HBM whereas SBM showed highest concentration at in April, 22.12 mg/L (Figure 3).
Both station showed variation in slected nutrients and opposite trend in nitrate, phosphate were observed. The high concentration of nitarate were estimated fom October- December at SBM. While nitrate lower cocentrations were obtained during some periods at HBM (Figure 3). Similar trend was noted in July.
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Table 1 showed the results of ANNOVA and regression analysis between station and nutrients. The stations are significantly different (P < 0.05) with respect to the nutrients. Showing relationship between the mangrove stations and between the non mangrove stations with respect to NH4 concentration.
Table 1. Regression analysis and one way one way ANOVA (P < 0.05) among stations with respect to the nutrient concentration.
NH4 NO3 PO4 R-sq(%) F P R-sq(%) F P R-sq(%) F P OC- HS 93.7 163.6 0 6 0.7 0.4 33.1 5.4 0.04 HBM-SBM 90.6 106.4 0 3.4 0.3 0.5 0.5 0.05 0.82 OC-HBM 27.2 4.1 0.06 5 0.5 0.4 27.9 4.2 0.06 OC-SBM 52.2 11.9 0.005 4.9 0.5 0.4 7 0.8 0.3
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Figure 2. Annual variations (September 2012- September 2013) in nutrients concentration at HS and OC
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Figure 3. Annual variations (September 2012- September 2013) in nutrients concentration at HBM and SBM.
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3.3. COMPOSITION OF ZOOPLANKTON AMONG FEEDING GUILDS IN MANGROVE FOREST
3.2.1. FEEDING GUILD PERCENT COMPOSITION AT HBM
The composition of zooplankton functional feeding groups was studied from September 2012 to September 2013 (Figure 4). Four functional feeding guild were identified. Omnivore zooplankton dominats the rest of the three feeding groups. 80% of the omnivore zooplankton from April to July and they were the most dominant group from April to July.
Herbivore zooplankton assemblage showed their high abundance in September 2012 and in August (45%). Strictly herbivore planktons were completely absent in June where as omnivores and detritivore planktons were present with their high abundance (74% and 29% respectively). Detritivore zooplankton were less abundant at HBM (Figure 4). Carnivore plankton group was with less than 5% composition from April to June. The highest (33%) composition of Carnivore zooplankton was recorded in November (Figure 4).
More than half of the space at HBM was occupied by the omnivore planktons. 32 % was covered with Herbivore. Only 8 and 4 % of the space was composed of carnivore and herbivore zooplankton respectively (Figure 4).
3.2.2. FEEDING GUILD PERCENT COMPOSITION AT SBM
At station SBM feeding guild percent was recorded annually. Omnivore s were found highest during May and July 97 and 96 percent respectively (in the total s count). This feeding guild was found with its least possession in February which was only 28%.
Herbivore feeding group of zooplankton showed high composition among other groups during September 12 and August (43 and 45% respectively). The least % composition was attained from May and July (2 and 1 respectively). No herbivore zooplankton was observed during June analysis.
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Carnivore feeding guild expressed its high % among other groups during November which was 35%. Least numbers was noted in May and July 1% and 3% respectively (Figure 5). With their ups and down presence in total zooplankton the carnivore feeding guild was found throughout the year.
The last feeding union of s, detritivore s was not as much of the total s. The highest possession of group was recorded in June with 14%.most of the time the group was absent during zooplankton analysis (Figure 5)
The total composition of the guilds was determined at SBM. The % composition illustrate the dominant habitant of this mangrove station was omnivore (56%) zooplankton as at HBM. Slightly higher percentage of omnivore group (59%) was noted as compare to HBM (Figure 6)
Detritivore and herbivore was slightly less in numbers at SBM as compare to the HBM inhabitants. To some extent omnivore and carnivore showed high percentage at SBM as compare to HBM (Figure 6).
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Figure 4. September 12 to September 13 percent variation in feeding groups of zooplankton in mangrove waters HBM.
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Figure 5. September 12 to September 13 percent variation in feeding groups of zooplankton in mangrove waters SBM.
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Figure 6.
Percentage composition of zooplankton feeding guilds at HBM and SBM.
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3.3. AUTOTROPHIC AND HETEROTROPHIC BIOMASS COUPLING
3.3.1. COUPLING PATTERN AT HS AND OC
In marine food web relationship between the heterotrophic and autotrophic groups mainly moves around the phytoplankton and zooplankton and provides the energy to the upper trophic ranks.
At HS variations in zooplankton biomass and phytoplankton biomass coupling was recorded. The high values for zooplankton biomass were recorded in September 12, February and in September 13. During November and September 13 the both of the concentration of zooplankton and phytoplankton biomass were equally high during September 13 (37.7g/m3 and 0.8µg L-1 respectively) and equally low during November (0.019 g/m3, 0.075µg L-1 respectively). Highest zooplankton biomass was estimated during September whereas phytoplankton biomass concentrated was reported high in May (Figure 7).
At OC the pattern of zooplankton and phytoplankton biomass distribution were reported differently from HS. Equally high and low values for both of the biomasses was recorded during December, March and September 13. Classical crossing of phytoplankton and zooplankton biomass was noted. The highest zooplankton biomass was obtained in February and the highest phytoplankton biomass was recorded in May and June (54 and 56 µg L-1) (Figure 7).
3.3.2. COUPLING PATTERN AT HBM AND SBM
Autotrophic and heterotrophic biomass in terms of phytoplankton and biomass was estimated from September 12 to September 13.
At HBM mangrove site the coupling was not reported in steady state. Where the biomass concentration of both trophic groups show their stability. Ups and down was reported with the inverse relation of and phytoplankton biomass. The highest biomass (0.70 g/m3) was noted during September 12 where phytoplankton biomass (0.05 µg L- 1) was present with its second lowest concentration as shown in Figure 8.
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At SBM slight equilibrium in the concentration of and phytoplankton biomass was noted only in January. During January both of the trophic groups showed closer concentration to each other as shown in Figure 8 The highest concentration of biomass was noted in December (0.93 g/m3) and highest phytoplankton biomass (74.9 µg L-1) was reported from SBM in May (Figure 8).
Figure 7. Yearly distribution of zooplankton and phytoplankton biomass at HS and OC.
Figure 8. Yearly distribution of and phytoplankton biomass in mangroves forest at station HBM and SBM.
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3.4. EFFECT OF NUTRIENTS ON PLANKTON
ANOVA and Linear regression was performed on the data to check the effect of nutrients on phytoplankton biomass.
At HBM phytoplankton biomass only showed its significance relation with ammonia. While phosphate and phaeopigment relation was significant. Biomass relationship between phytoplankton and was also significant. Whereas at SBM nitrate and phaeopigment relation was determined as significant relation. Total abundance of zooplankton showed significant relation with phytoplankton concentration at SBM (Table 2).
Table 2. Regression analysis and one way ANOVA (P < 0.05) for the nutrient concentration with respect to phytoplankton and zooplankton biomass. And total zooplankton abundance with Phytoplankton biomass.
HBM SBM R-sq R-sq (%) F P (%) F P NH4-phytoplankton 9 1.09 0.31* 12 1.5 0.24 biomass NO3-Phytoplankton 4.3 0.5 0.49 0.4 0.05 0.8 biomass PO4-phytoplankton 1.1 0.12 0.73 7.7 0.9 0.35 biomass NH4-Phaeopigments 2.2 0.25 0.62 5.1 0.59 0.46 NO3-Phaeopigment 1.1 0.1 0.76 23.3 3.35 0.09* PO4-phaeopigment 29.8 4.6 0.05* 2.6 0.29 0.59 Phyto-zooplankton 7.1 0.85 0.37* 1 0.11 0.74 biomass Zooplankon- 5.2 0.61 0.45 16.7 2.2 0.1* phytoplankton
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3.5. MANGROVE TIDAL CYCLE
3.5.1. ASSESSMENT OF HYDROLOGICAL PARAMETERS DURING TIDAL CYCLE
During a complete tidal cycle at HBM fluctuation in all physical variables were recorded during tidal cycle. Temperature variation recorded noted from 30-32.3oC. The high Temperature was found during MT (Figure 9). Salinity of the sea water during tidal cycle showed no significant variation was recoded. Salinity ranged between 40-40.5 ppt (Figure 10). The pH ranged between 7.3- 8.0 during tidal cycle. Highest pH was recorded at HT (Figure 11). DO was ranged from 2.3-9.9 mg-L-1. The high concentration of dissolved oxygen was noted at HT (Figure 12). High transparency of station HBM was recorded during HT (1m). TSS showed high values during both of the tides (0.17 mg-L-1 and 0.19 mg-L-1) during LTd and LTn respectively (Figure 13).Significant relation was noted in tidal height with pH, TSS, transparency and DO (Table 3) The DO showed significant variation during tidal cycle (F=11.4, P=0.07). Biological parameters also showed significant variation. Phytoplankton biomass showed significant relationship with nitrate as compare to other nutrients. Significant relationship between phytoplankton and zooplankton biomass was observed during tidal cycle (Table 4).
Figure 9. Temperature variation at four tides during a complete tidal cycle. 136
Figure 10. Salinity change at LT, HT and MT during a complete tidal cycle.
Figure 11. Tidal variation in pH during a complete tidal cycle.
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Figure 12. DO variation during complete tidal cycle.
Figure 13. TSS and transparency relation at all four tides of a complete tidal cycle.
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Table 3. Regression analysis and ANOVA (P < 0.05) between tidal heights and different hydro biological factors.
Table 4. Regression analysis and ANOVA (P < 0.05) for nutrient concentration with respect to phytoplankton and zooplankton biomass during a complete tidal cycle.
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3.5.2. ASSESSMENT OF PHYTOPLANKTON AND ZOOPLANKTON COUPLING
Coupling between the phytoplankton and zooplankton biomass was recorded during complete tidal cycle (Figure 14). Phytoplankton biomass was high as compare to zooplankton biomass at LTd and MT. At HT zooplankton biomass was high and phytoplankton biomass was low. LTn the both of the biological biomasses showed same pattern of occurrence.
3.5.3. ASSESSMENT OF NUTRIENTS DURING TIDAL CYCLE
Ammonia, Nitrate and Phosphate concentration between the tides showed different pattern (Figure 15). All three nutrients was recorded with same distribution during LTd which was followed by the decreasing trend in HT. during MT phosphate was very high (29 mg.L-1) as compare to other nutrients. Decrease in Phosphate concentration was noted in LTn.
Figure 14. Tidal variation in zooplankton and phytoplankton biomass coupling.
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Figure 15. Distribution of nutrient concentration at all four tides during a complete tidal cycle.
3.5.4. ZOOPLANKTON COMMUNITY COMPOSITION
During tidal cycle 9 groups of Mesozooplankton were recorded. 41.1% of total MZ was occupied by copepods and rest of 58.8 was other groups which include coelenterate, nematodes, gastropods, crustacean larvae, ostracod and appendicularians. Percentage composition of MZ in complete tidal cycle was high at HT then at LTn which was followed by LTd (Figure 16). The lowest percentage of zooplankton was recorded at MT. Calanoid was abundant among copepods in all tides with 2049 Ind.m-3. The pattern was followed by cyclopoid and then herpacticoid with 599 Ind.m-3 and 166 Ind.m-3repectively. Calanoid copepods were the most abundant group at HT whereas nematodes dominates during LTd and LTn. Appendicularian were only recorded at HT and MT (Figure 17).
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3.5.5. FEEDING GUILD PERCENT COMPOSITION IN TIDAL CYCLE
Functional group was formed on the basis of their feeding habits. Ominvore zooplankton was found high (48%) during complete tidal cycle at LTn. Herbivore zooplankton was present with 35% whereas the least abundant feeding guild was Carvivore (Figure). During LTd and LTn detritivore zooplankton was dominated with 56% and 50 % respectively as compare to other feeding guilds. In HT and MT Omnivore was dominated with 40 % and 47% respectively (Figure 18).
Figure 16. Percentage composition of zooplankton during LT, HT, MT and LTn.
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Figure 17. MZ group abundance (Ind. m-3) during Tidal cycle.
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Figure 18. Functional group distribution during tidal cycle. (a) Feeding group composition at LTd (b) feeding group composition at HT (c) feeding group composition at MT (d) feeding group composition at LTn. 144
3.5.6. PLANKTON TROPHIC ENERGY FLOW IN MANGROVES
At mangrove stations HBM and SBM trophic interaction between planktons were estimated by making pyramids of abundance. At HBM and SBM annual mean production in terms of Chl a concentration was recorded as 21.30 and 25 mg/m3 respectively. At HBM from producer the energy was transferred to the 3692 Ind-m-3 (average) herbivore zooplankton. Whereas from SBM 3291 Ind-m-3 (average) of herbivore zooplankton were recorded (Figure 19). Omnivore zooplankton were the most abundant zooplankton as compare to herbivore at both HBM and SBM. The mean density of omnivore zooplankton was 6482 Ind-m-3 and 6643 Ind-m-3 at HBM and SBM respectively. Energy transfer from producers to consumers and from detrivores to consumers shown in abundance pyramid (Figure 19).
During Tidal cycle inverse abundance pyramids was formed at LTd and LTn (Figure 20 a, b). Phytoplankton biomass was high at both low tides but herbivore zooplankton was lower in density (Figure 20). The detritivore zooplankton was highest in density at both LTd and LTn (700 and 966 Ind-m-3 respectively). Carnivore zooplankton were not recorded at HT and MT and omnivore and herbivore zooplankton were recorded in high density at both HT and MT.
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HBM
SBM
Figure 19. Annual Trophic energy flow among planktons at HBM and SBM.
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LTd
HT
Figure 20a.Trasfer of trophic enegy at LT and HT during a complete tidal cycle.
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MT
LTn
Figure 20b. Trasfer of trophic enegy at MT and LTn during a complete tidal cycle.
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4. DISCUSSION 4.1. NUTRIENT DYNAMICS AND PLANKTON
PRODUCTION
Effluents from industrial waste and domestic sewage dumped into the Manora channel through layari river (WWF, 2002). The nitrogen containing nutrients NH4 and NO3 was recorded high at HS. This station is close to Layari River outlet and thus receives the large amount of nitrogenous compounds from Layari River
(JICA, 2007). At HS and SBM highest concentration of NH4 were recorded during August which is the same as reported in previous study for nitrogen nutrients conducted in Manora channel and mangrove forest (Harrison et al., 1997; Shoaib et al., 2017). Estuarine ecosystem and coastal ecosystems are the most vulnerable to these outputs which receives 1000 time greater nutrient input as compare to the nutrient rich agriculture grounds (Nixon et al., 1986). Estimation of nutrient from mangrove stations reveals high load of NH4 and NO3 at HBM station. These nutrients are the main factor which enhance the phytoplankton growth (Saifullah, 2016). Phosphorous concentration was recorded high at OC and HBM which may be because of the PO4 flux through tidal effect in Manora channel. From Manora 12000 tons of phosphate compounds has been reported which eventually increase the concentration of phosphate (JICA, 2007). During this study at HBM the significant relation was noted for phytoplankton biomass with NH4 concentration and all the nutrients was significantly correlated with phaeopigments in mangrove stations. Te utilization of NH4 by small phytoplankton was reported by Malone, 1980. This indicates that which means mostly population of phytoplankton in this study area consist of planktons.mall size. The higher phytoplankton biomass was recorded at station where low concentration of NH4 was observed which showed the utilization of nutrients by phytoplankton. During June NH4 was low and increasing phytoplankton biomass was observed and in August both the NH4 concentration and phytoplankton biomass was high which proves that nutrient mainly NO3 and PO4 are essential for high primary productivity which have been reported to have direct relation with nutrients (Saifullah et al., 2014). The less abundance of zooplankton in mangroves might be because of the eutrophic
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condition which ultimately disturbed the zooplankton and other living organism (Smayda 1992). The energy transfer through nutrients to the phytoplankton and ultimately transfer to the herbivore consumers and then to higher trophic levels is previously reported (Dickman et al., 2008) although the low concentration of nutrients are not a sole limiting factor to the phytoplankton growth (Marra and Barber, 2005). Fluctuation between both the phytoplankton and zooplankton biomass has reported in this study. The high phytoplankton were recorded from OC, HBM and SBM whereas HS posses low phytoplankton biomass. The low phytoplankton biomass is due to the presence of high zooplankton biomass indicating grazing pressure upon sufficient availability of phytoplankton and other prokaryotes (Sherr and Sherr 2002). Mixing of dissolved nutrinets by tidal currents and stroms supported the blooming of phytoplankton production between April and May. The peak Production was reported to occur primarily as spring bloom in spring season (April–May) (Bond and Overland, 2005). The low concentration of phytoplankton biomass was recorded in November where as
during same periods the high concentration of NH4 and low concentration of NO3 was recorded besides this the low values of dissolved oxygen was recorded in November thus the high concentration of dissolved oxygen promotes the
coversion of NH4 to NO3. It has been reported that the large sized phytoplankton are more abundant in Manora channel as compare to the open Ocean (Naz et al., 2013). It proves the presences of large sized plankton in this area as small phytoplankton groups give less attention to the Nitrates (Malone, 1980). Phosphate concentration was raised during sufficient phytoplankton biomass period which reveals the low consumption by micro plankton. Beside other factors phosphorous also increase the zooplankton reproduction (Pitta et al., 2016).
4.2. TROPHIC INTERACTION BETWEEN THE ZOOPLANKTON FEEDING GROUP
To study the interaction between mesozooplankton, they were grouped on the basis of previously cited literature into four feeding group which includes Herbivore, Carnivore, Omnivore and Detritivore. Coelenterate and Ctenophores are carnivores which mainly feed on copepods (Larson, 1987; Purcell, 1997). Chaetognaths were
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designated as carnivore with high lipid content in gut (Grigor et al., 2014). Group lucifers and fish larvae are zooplanktivorous the exhibit carnivorous type of feeding (Morotte et al., 2010; Lee et al., 1992). Copepods are the most abundant metazoan in our Ocean. Copepods are opportunistic feeder and are omnivorous in their feed selection. Cannibalism is also been reported in calanoid copepods which feed on small nauplii if they face shortage of feed (Dann et al., 1988). Some of cyclopoid species start grazing on diatoms when there is low numbers of microzooplankton available for their feed (Vogt et al., 2013). Feeding of copepods ranges from detritus feeders to omnivorous (Benedetti et al., 2015), Cladocerans are herbivorous in their food selection they mainly feed on diatoms (Kim et al., 1989). Ostracods are omnivore (Athersuch et al., 1989). Salps doliolids and appendicularian are filter feeders except this mechanism pelagic tunicates mainly feed on phytoplankton and are herbivores (Alldredge and Madin, 1982). Molluscan larvae are also herbivore but in some cases they rely on bacteria (Martin and Mengus, 1979). Amino acids were reported from the gut content of the larvae (Manahan and crisp, 1983), but typically they depends on phytoplankton in water column (Raby et al. 1997). Echinoderm larvae feed on phytoplankton and some other food particles and specifically they are herbivore in nature (Richard, 1975). Polychaete larvae are carnivore they feed on copepods and other small zooplankton. (William et al., 2012) Nematodes feed on organic detritus in shallow waters and majority of them are detritivore in nature (Armenteros et al., 2010). The omnivore were the most abundant group at both mangrve stations and play important role in the cycling of energy between trophic level.
4.3. MANGROVE TIDAL CYCE AND HYDROLOGICAL CONDITIONS
Mangrove ecosystem mainly receive influence from tidal energy by tidal water flux (Costa-Böddeker et al., 2016). Tides bring nutrients in and out of the mangrove forest. Salinity, dissolved oxygen, change in nutrient concentration observed beween tidal fluctuation. Temperature difference of 2 oC was recorded during tidal cycle. Another study reported the daily change in 2-4oC temperature is (Kim et al, 2010). The high temperature low concentration of H ions and high salinity was recorded during MT.
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Salinity is the key factor for the biota of estuarine system which increases in dry season. High salinities are attributed to the high evaporation which is ultimately the caused by high temperature which is the agreement of present readings (Wolanski, 2007; Uncles and Stephens, 1996). Estuarine waters are highly turbid and has reported to less transparent because of the nutrients and suspended particles (Dawes, 1981). The high turbidity in mangrove was reported due to the leaching from litter production. Highest turbidity at LT is due to flow of ebb tides which brings nutrient and other detritus from mangrove. The higher concentration of DO is due to the low temperatue and flux of oxygen rich water from the mouth of Manora channel towards HBM. Mangrove habitats are typically oxygen deficient environment due to high production of organic matter (). Lower concentration of dissolved oxygen at LT indicates utilization of dissolved oxygen for the break down of organic matter which results in low oxygen in the receiving tide. Carstensen et al., 2014 stated that high temperature effects the dissolved oxygen concentration inversely. Although high transparency favours the phytoplankton concentration by providing light upon the availability of nutrients (Sugimoto and Tadokoro, 1997). But in present study lowest phytoplankton biomass and high clarity of water at HT was recorded which must be due to the lower availability of nutrients at HT. High tide cycle in manora channel brings wave of water in the mangrove forests of sandspit back waters and drain the detritus and other organic matter to the open Ocean.
For the production phytoplankton biomass nutrient should be in adequate concentration lower than required concentration of nutrients also limits the phytoplankton growth (Rahaman et al., 2013). The lower concentration of nutrients at HT ultimately results in low Chl a concentration. Similarly high nutrients concentration at MT was a result of receiving tide which bring nutrients rich water from mangrove forest and than available to phytoplankton which utilize this nutrients resulting in the less concentration at LT. Present study shows the significant relationship of tidal height with salinity, pH, DO, phytoplankton biomass and nutrients such as NO3 and NH4. Tidal height variation urges the mixing of nutrients in mangroves which ultimately enhance the mixing of DO and enhance the primary productivity (Harrison etal., 1997). The variation of phytoplankton and zooplankton biomass with the tidal movement is attributed to the mixing of nutrient and
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availability of nutrient. Primary production relay on light so that the high primary production has been reported during day as compare to the LTn.
4.4. FEEDING GUILDS COMPOSITION IN TIDAL CYCLE
Total zooplankton were recorded high during HT and Ltn. During high tide strong tidal influx brings the zooplanktons in mangroves. The zooplankton migrated towards surface during night. As the high density is reported for night samples as compare to the day (Vu et al., 2017; Darnis et al., 2017).
Functional feeding groups in mangrove waters mainly depends on the availability of suitable food sources. With the changes in tides the food particles moves to and from mangroves. The high percentage of detritivore zooplanktons at LTd and LTn indicate the movement of detritus from mangrove forest. Which comes out from mangrove litter production by the tidal outflow from mangrove (lee et al., 2014). This detritus was consumed by the detritivore zooplankton which results in to increase density of detritivore at LTs. In mairne ecosystem it is very difficult to find the feeding interaction and trophic status for each single species especially among plankton. The plankton food web have key position in energy transfer. Phytoplankton production leads the primary consumption by zooplanktons. Among zooplankton four groups showed the interlinked energy pattern within the mangrove ecosystem (Vu et al., 2017). Classical pyramid was obtained on the basis of density of plankton annually from mangrove station. Where primary production consumed by herbivore zooplankton which further being consumed by the omnivore. Some omnivore consumed by the strict carnivore groups like Cheatognaths.
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5. CONCLUSION
This chaphter conclude that the nutrient energy flux of main nutrients NH4, NO3 and
PO4 showed annual and tidal variation between the station NO3 and NH4 was reprted to found with high concentration at HBM an OC whereas the PO4 high concentration was recorded high at OC. High chl a concentration showed significant relation with NH4. Within the trphic pyramid the high dense group was found for omnivore zooplankton. The least abundant trophic group was detritivore. The tidal fluctuation showed the high inorganic nutrients in MT where the Phytoplankton was also high. Inverted energy pyramid during LTs. And classical pyramid was noted for HT and MT. the change in zooplankton and phytoplankton biomass was found to be variate with dancing tides. But not only nutrients are the key factor for the phytoplankton production it seems that all the physical variables are collectively responsible of Phytoplankton and zooplankton biomass.
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DISSERTATION CHAPTER # 5 DISCUSSION
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GENERAL DISCUSSION
Present research was conducted to estimate the mangrove energy flux on mesozooplankton (MZ) group abundance. Physical changes, such as turbidity, tidal variation and monsoonal wind reversal of current was reported to influence the biological activity of the ecosystem (Harrison et al., 1977). The part of Arabian Sea along the Pakistani coast was reported as highly dense in zooplankton and phytoplankton population (Baranova et al., 2009). Phytoplankton utilized the nutrients to compete the reduction by grazing. Zooplankton have been showed to regulate the fishery of the area (Stottrup, 2000) and have special position in fisheries management.
Annual abundance of 21 mesozooplankton groups were recorded at mangrove stations and at two non- mangrove stations. A total of 1604136 individuals of mesozooplankton including copepods were recorded during this study. The highest density of mesozooplankton excluding copepods was recorded at OC (291418 Ind.m- 3) which was followed by HS, HBM and SBM (226900, 136401 and 123900 Ind.m-3) respectively. Copepods was the most dominant (61 %) as compare to other mesozooplankton (39%) with a total of 843082.4 Ind-m-3 during the study. From Pakistani waters Naz et al., 2014 has reported 66% and 74 % of total copepods from two different sites. Higher zooplankton from off shore waters has reported (Kidwai and Amjad, 2000). Another study from China also showed the dominancy of copepods (Chen and Lio, 2015).
Seasonally, the high diversity of mesozooplankton was recorded during SWM and lowest during POM seasons at all stations. Similarity the high density was noted in SWM and NEM. From Arabian Sea it has been reported that monsoonal season bring strong effect on zooplankton community and its dynamics (Wishner et al., 2000). The number of biotic and abiotic processes were reported to effect the distribution of zooplankton. A single factor does not appear to control the diversity and density of mesozooplankton in present study. The temperature, salinity, dissolved oxygen, pH, tidal height and availability of food appears to control the distribution of zooplankton. In mangrove forests these parameters were mainly effected by external factors such as
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fresh water influx, tidal inflow and outflow from the mangrove sites (Gowda et al., 2001).
Cladocera was the dominant taxa after copepods in terms of abundance and Penilia avirostris was recorded abundantly in samples and their highest density was recorded in October. From other part of the world the high density of cladocerans reported during winter and autumn and low in summer (Champalbert, 1996). The dominance of cladocerans after copepod was also reported from South China Sea (Li et al., 2014). In the present study, Chl a and salinity was found to control the cladoceran abundance and same has been reported by Marazzo and Valentin, 2004. Penilia avirostris is commonly distributed in tropical and subtropical areas and reported to play vital role in the microbial loop (Katechakis and Stibor 2004; Rose et al., 2004).
Ctenophores were high in abundance at OC and at HS. Gelatinous zooplankton showed their significant relation with temperature and Chl a, as they mainly feed on phytoplankton (Flores et al., 2012; Whitehouse et al., 2008). Nematodes showed significant correlation with salinity and the correlation between salinity and nematodes were described from mangrove waters (Heip et al., 1985). The concentration of dissolved oxygen, organic matter and Chl a, was also reported to effect the nematode distribution.
This is the first through study on the abundance and community structure of copepods. Earlier research on zooplankton from Pakistani waters were contributed by Masihuzzaman, 1973; Haq et al., 1973; Ali-Khan and Hempel, 1974; Ali-Khan and Ali-Khan, 1978; Muniza and Kazmi, 1995; Naz et al., 2012. The work on copepod abundance and community structure were raised just up to the group level. Not sufficient species abundance records were found in literature except the Haq et al., 1973, Khan, 1974 and 1979. Haq et al., 1973 give the account of 16 planktonic copepods species and their abundance from Pakistani coastal waters. A total of 69 species of copepods under the four orders and 21 families were identified in the present study. The Order Calanoida (47 species) were the dominant order throughout the study period which constitute the major part of copepods community as these mini creatures have been designated as the most abundant life in marine ecosystem (Humes, 1994). The highest calanoid occurrence has been reported from the other parts of the Oceans as well as from estuarine ecosystems (Haq et al., 1973; 157
Madhupratap and Haridas 1986; Kibirige and Perissinotto, 2003; Yamaguchi et al., 2004; Champalbert, et al., 2005; Leandro et al., 2007). Temoridae, Paracalanidae and Pseudodiaptomidae were the most dominant family in our study area. T. turbinate. A. longicornis and Pseudodiaptomus serricaudatus were the main representative of these families in terms of high abundance (Ara, 2002; Haq et al., 1973). Cyclopoida were the second abundant group after calanoids (17 species). Corycaeidae, Oithonidae and Oncaeidae were the most dominant. Harpaticoida was abundantly found with the family Euterpinidae represent only one species Eterpina acutifrons.
Seasonal variations was recorded on the copepods community structure. Like other mesozooplanktons, seasonal pattern the copepods also showed high abundance in SWM which reveals that the SWM is favourable to copepods for growth. This pattern of distribution agreed with the results given by Khan, 1979. After 3 decades, despite of changes in environmental conditions, the SWM is still a favouring season for copepods abundance. During all seasons the Calanoids were dominant followed by cyclopoid, harpacticoid and monstrilloid. Exceptions was noted in PRE-monsoon season where copepods community was dominated by the cyclopoid copepods. Seasonal variations were recorded in copepods abundance. Similar results were given by Yaqoob et al., 2013.
Out of 69 species 23 species was reported for the first time from Pakistani waters. 6 species are published from this study which belongs to the genus Oithona (Ara et al., 2017) and 2 species was published during this study which belongs to the genus Corycaeus (Ara and Farooq, 2013). Overall the mangrove stations HBM and SBM were different with respect to copepods species diversity and density.
Mangroves are preferable areas for many species as they serve as nursery and sheltered sites for the larvae of many fish and crustaceans (Robertson and Duke, 1987; Sasekumar et al., 1992). The effect of mangrove energy flux was studied at mangrove stations along with the tidal cycle to see the tidal influence on nutrients and biotic variables. High concentration of NH4 and NO3 was found at HBM. The high concentration of Chl a at at mangrove stations indicates high phytoplankton biomass. Which agreed the statement that nutrients are the main source to phytoplankton reproduction (Saifullah, 2016). The high phytoplankton biomass was recorded where
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low concentration of NH4 was observed this indicates the utilization of nutrients by phytoplankton.
PO4 concentration was recorded high at OC and HBM which may be because of tidal effect in Manora channel. From Manora 12000 tons of phosphate compounds has been reported which eventually increase the concentration of phosphate (JICA, 2007). Between OC and HBM tidal movement of waters fluxes the nutrient (nitrogen and phosphorous) between these stations. It has been recorded that from Lyari River the waste waters bring nitrogen and phosphorous compounds into the channels and with tidal flow these nutrients moves from inshore to the offshore sites.
The higher Total suspended solids (TSS) at station HS and SBM indicate the turbid water due to the drainage of sewage through Lyari River near station HS. The data indicates that the SBM receives influence from HS during ebb tides. The higher values of TSS was reported to inhibits the mixing of dissolved oxygen which simultaneously disturbed the zooplankton and other living being by low oxygen availability (Smayda 1992).
The zooplankton at high tide reflect the high presence of grazers. Four feeding guilds were formed in which the omnivore were recorded high and the less number of detritivore zooplankton was noted at both mangrove stations. The migration of different larvae into mangrove areas for feeding and sheltering purpose mainly depend on the tidal currents (Sheaves, 2003). The grazers enter with the high tide into mangrove forests for feeding. Among zooplankton trophic interaction the feeding behaviour of zooplankton group are very important. The energy flow from one trophic level to the other formed the classical pyramids linked energy flow (Vu et al., 2017). Phytoplankton are the main component of carbon cycling whether they sink down or transfer it to zooplankton which also transfer the organic carbon to the ocean directly (Treguer et al., 2018).
During tidal cycle in mangroves, the nutrient (NH4) and phytoplankton biomass was noted high during mid-tide (MT). During high tide (HT) the leaching from mangroves forests enters in the overlying and surrounding waters which soon becomes available to phytoplankton at mid tide (MT), thus, increasing their numbers. Although nutrients play crucial role in phytoplankton production, other factors such as pH, dissolved
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oxygen, salinity and temperature also reported to effect phytoplankton biomass (Rajasegar, 2003; Ning et al., 2004). Inverted pyramids was formed at both LT night and LT day, where the detritivore zooplankton was high. The receding tide from mangroves also increases the detritus which attracts detritus feeders at low tide. The higher abundance of zooplankton abundance at HT and Ltn proves the DVM phenomena in zooplankton.
This study reveals that the energy flux through nutrient and detritus flow from mangrove forests are influencing zooplankton density in surrounding areas. The higher phytoplankton biomass at mangrove stations provide food to herbivore and omnivore zooplanktons. The data indicates similarity between station OC and HBM, whereas the station SBM receives influence from HS.
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FUTURE RECOMMENDATIONS
I will suggest the further study should be done on deeper waters to evaluate the MZ community and the influence of different variables.
With the passage of time the advancement in techniques are being developed for zooplankton studies. DNA sequencing of copepods species is the hot topic in copepods research. Further studies are required on DNA sequencing of the copepods species to compete the advance reseacrh.
Further systematic work is required to evaluate the species diversity of other zooplankton groups
Parasitic invasion on copepods should be diagnose for further study on copepods dynamics and their potential role in fisheries.
I will propose the further exploration of Pakistani coastal waters to compete the research on zooplankton and their role in ecosystem.
Taxonomic key should be maintain to encounter the resident species and further study on these species to evaluate their role in energy transfer.
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