Surface Zooplankton Sogod bay

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Surface Zooplankton Community Composition in Whale shark

(Rhincodon typus) Feeding Grounds Off Sogod Bay, Southern Leyteduring August 2013 to March 2014

by

PAUL MATTHEW L. MUNCADA

A research paper submitted to the

Division of Natural Sciences and Mathematics

University of the Philippines Visayas

Tacloban College, Tacloban City

As partial fulfillment of the requirements

for the Degree of

B.S. BIOLOGY

May 2014

Permission is given for the following people to have access to this research:

Available to the general public Yes

Available only after consultation with author/adviser No

Available only for those bound by confidentiality agreement No

Students signature:

Signatur e of Research Adviser :


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This is to certify that this research paper, entitled: Surface Zooplankton

Community Composition in Whale shark (Rhincodon typus) Feeding GroundsOff Sogod Bay, Southern Leyte during August 2013 to March 2014 and

submitted by PAUL MATTHEW L. MUNCADA to fulfill part of the requirements

for the Degree of Bachelor of Science in Biology is hereby endorsed.

LENI G. YAP-DEJETO

Research Adviser

The Division of Natural Sciences and Mathematics (DNSM) accepts this

research paper in partial fulfillment of the requirements for the Degree Bachelor of

Science in Biology.

ROBERTO E. CAPON

DNSM Chair


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ACKNOWLEDGEMENT

I would like to express my deepest gratitude to all the people who have guided

me to achieve the accomplishment of this research:

to my adviser, Prof. Leni Yap-Dejeto, for suggesting and entrusting this study

to us. We would have never been able to make it if not for her valuable advices and

support throughout the study period from the proposal up to the oral presentations;

to the LAMAVE Project researchers, especially to Ms. Jessica Labaja, and to

their project head, Dr. Alessandro Ponzo, for their kindness and willingness to help

every time we visit Pintuyan despite their hectic research schedules;

to Pastor Ernesto Felicio, kuya Gerry, Mr. Virgilio Flores and the whole

barangay of Son-ok dos, for being so accommodating and for providing us motor

boats;

to Mr. Rey Verona, for letting us borrow laboratory instruments;

to Mr. Joseph Dominic Palermo, for answering our questions regarding

zooplankton and confirming the zooplankton we identified;

to kuya James Ostrea and ate Kim Ruizo, for the help during our first

sampling and additional information regarding the methods of this study;

to Ms. Sharmaine Ida, for the company, assistance and shared struggles during

the whole study period;

to Ms. Retsie Corado, Mr. Daniel Licayan, Ms. Pearl Joy Angelie Sigua and

ate Coleen Alonzo, for the shared plankton experiences and overnights;

to Mr. John dela Cruz and Mr. John Paul Ada, for the help during the final

stages of this research paper;


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to Ms. Haide Batula, who has always been there for me like the phytoplankton

for the zooplankton;

to my family, who never stopped believing and prayed for me always; and,

most importantly, to God, for these great people above and all the blessing He

bestowed upon the duration of this study.


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v

ABSTRACT

Sampling stations in the study site off Sogod Bay, Southern Leyte were

established along the feeding grounds of whale shark (Rhincodon typus). The whale

shark season in the area is known to last from November to July. Water samples and

physico-chemical parameters from three sampling stations were taken and collected

once a month in August and October in year 2013 within the off whale shark season

period, and March 2014 within the whale shark season. Abundance, composition, and

diversity of zooplankton groups encountered were quantified. Copepods dominated by

66% (Order Calanoida 26%, copepod nauplius 16%, Order Cyclopoida 14% and

Order Harpacticoida 10%) of the total zooplankton population. October 2013 had the

least mean density of 1.9x103 ind./L. August 2014 samples had the least zooplankton

diversity of H= 1.58. Samples obtained during the whale shark season, March 2014,

showed the highest total zooplankton abundance at 7.7x103 ind./L. This also yielded

the highest zooplankton community diversity of H= 2.53.


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TABLE OF CONTENTS

Page

Acknowledgements... iii

Abstract ........ v

List of Tables.... viii

List of Figures.......... ix

Introduction... 1

Literature Review........ 3

Importance of Zooplankton in Marine Communities.. 3

Marine Zooplankton in Southeast Asia... 4

Rhincodon typusand its Feeding Habits.. 4

Rhincodon typusin the Philippines.... 6

Sogod Bay, Southern Leyte.... 6

Methodology... 8

Study Site.... 8

Physico-chemical Analysis.. 8

Collection and Preparation of Samples... 10

Zooplankton Identification.. 11

Cell Density Determination. 11

Data Analyses.. 12

Results.. 13

Zooplankton Abundance and Composition. 13

Quantitative Analysis.. 13

Qualitative Analysis 17


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Zooplankton Diversity. 17

Physico-chemical Parameters...... 18

Discussion.... 21

Zooplankton Abundance off Sogod Bay, Southern Leyte.. 21

Diversity and Composition of Zooplankton Groups off

Sogod Bay, Southern Leyte. 22

Zooplankton Abundance and Diversity per Sampling Station 23

Conclusion...................................................................................................... 24

Recommendation......... 25

References.... 26

Appendix......... 29


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LIST OF TABLES

Page

Table 1. Zooplankton groups observed off Sogod Bay, Southern Leyte. 14

Table 2. Summary of physico-chemical parameters during August (2013),

October (2013) and March (2014) sampling in Sogod Bay,

Southern Leyte, Philippines. 20


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LIST OF FIGURES

PageFigure 1. Sampling Stations off Sogod Bay, Southern Leyte from

August 2013 to March 2014... 9

Figure 2. Zooplankton composition and density in Stations 1, 2 and 3 in the

sampling months August and October 2013, and March 2014 off

Sogod Bay, Southern Leyte...... 15

Figure 3. Mean zooplankton abundance in the months of August and October

2013, and March 2014 off Sogod Bay, Southern Leyte ... 16

Figure 4. Actinotrocha larvae from Family Phoronidae of Phylum Phoronida

in Station 2 during March 2014 sampling.... 17

Figure 5. Zooplankton diversity (H) in Stations 1, 2, and 3 in the months of

August and October 2013, and March 2014 off Sogod Bay,

Southern Leyte.. 18


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INTRODUCTION

Zooplankters are essential in every marine community because of their

richness and number. The most prominent zooplankton, the copepods, is regarded to

be the most abundant multicellular animals on Earth (Schminke 2007). Zooplankton

communities are proven to have high diversity and thus perform a variety of

important ecosystem functions and roles especially in aquatic food webs. They are

considered to make up the trophic level of primary consumers which makes them

critical to the functioning of ocean food webs (Richardson 2008).

Almost all of zooplankton preys upon the primary producers, the

phytoplankton. They also feed on other zooplankton groups (e.g. medusae), fish eggs

and larvae in their diet. They are in turn preyed upon by bigger fish larvae and many

adult planktivorous fish. The position of zooplankton in the food web is thus between

primary producers and predators. Zooplankton serves as a link between bottom-up

climate-related control of phytoplankton and fish and paves the pathway for energy

transfer from primary producers to consumers at higher trophic levels (Lalli and

Parsons 1997,Ayon et al. 2008,Richardson 2008).

Large animals in the ocean such as filter-feeding sharks and whale rely solely

to feed on plankton and small fishes (Richardson 2008). The whale shark or

Rhincodon typusis one of three species of large pelagic sharks that rely on plankton

and small nekton as their food source (Colman 1997). Whale sharks have two feeding

strategies; passive sub-surface ram-feeding and active surface feeding (Gudger 1941).

Passive feeding involves opening of the mouth while swimming and filtering water in

its path. Active surface feeding on the other hand makes use of a suction filter-feeding


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mechanism that sucks in and filters water while remaining still (Gudger 1941). These

kinds of feeding behavior makeR. typus dependent on densely populated patches of

plankton (Heyman et al. 2001).

Whale sharks are migratory and are known to inhabit tropical and warm

temperate water (Stacey et al. 2008). This includes Philippine waters as site of whale

shark migrations (Barut et al. 2003) . There are reports of whale shark sightings at

Donsol and Bohol Sea (Alava and Cantos 2004)and recently, Sogod Bay, Southern

Leyte (Bochove et al. 2007). The sampling stations established in Sogod Bay are

feeding grounds of whale sharks suggested by Dr. Alessandro Ponzo, president of

Physalus, a non-profit organization. Physalus conducts the LAMAVE (Large Marine

Vertebrate) Project in the Philippines which aims to raise environmental awareness of

large marine vertebrates through scientific research.

This research will provide baseline data of the abundance of zooplankton

species that the Rhincodon typus feed on along its migration path in Sogod Bay,

Southern Leyte. It will also serve to validate the hypothesis that these areas are

feeding grounds of the whale shark, Rhincodon typus. Consequently, this study has

the following objectives:

1. To identify the zooplankton groups present in the study site; and

2.

To quantify the abundance and diversity of zooplankton present in

the feeding ground off Sogod Bay, Southern Leyte.


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LITERATURE REVIEW

Importance of Zooplankton in Marine Communities

Microscopic animals that are found in bodies of water are known as

zooplankton. They take part in the marine food web and are essential in the study of

marine ecology and diversity. Zooplankton communities are considered to have high

diversity. The most prominent zooplankton, the copepods, is regarded to be the most

abundant multicellular animals on Earth. Copepods, by possibly three orders of

representatives, are able to outnumber the insects (Schminke 2007).

Restrictions in the swimming capabilities of zooplankters make these

organisms be carried easily by the water current. Thus, zooplankters are grazed upon

and eaten by planktivorous organisms since they are an easy prey and are usually

found in patches (Nybakken 1982). Zooplankton species acquire energy in different

ways. Different species of zooplankters employs a variety of carnivory, herbivory,

omnivory, and detritivory. With wide food choices available for these organisms,

zooplankton are among the primary consumers of the marine food webs and are

considered as key organisms, playing an important role in energy transfer and a link

to nutrients from the producers to bigger organisms such as fishes (Lalli and Parsons

1997,Ayon et al. 2008,Richardson 2008).

In addition, zooplankton such as larvaceans, copepods, and euphausiids are

capable of reprocessing marine snow and other nutrients eaten into much dense and

larger fecal pellets (Wilson et al. 2013). These nutrient packed pellets sink faster

down the water column, which is exported to be eaten by other organisms below

(Turner 2002).


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Zooplankton takes part in the biogeochemical cycling processes especially in

the carbon cycle in the ocean since they expend carbon for their respiration processes

(del Giorgio and Duarte 2002). In a study conducted by Hernandez-Leon and Ikeda

(2005), it was found that more than one-third of the organic carbon flow in the ocean

is contributed by mesozooplankton through cycling that makes up to a 1732%

respiratory loss of photosynthetic carbon produced in the open ocean.

Marine Zooplankton in Southeast Asia

Southeast Asia has a high species diversity of macro fauna because of this

regions unique settings. In fact, Southeast Asia is referred to as the worlds center of

marine biodiversity. To prove this, an estimate of more than 550 species or one fourth

of the total species of pelagic copepods are identified and are known to inhabit this

region. The discoveries and count of zooplankton are still growing in this region.

Twenty-nine planktonic copepods and 16 mero-planktonic or non-planktonic

copepods, 4 amphipods, and 2 isopods were described as new to science in recent

studies and an additional of 37 species of mysids were described as new from

Southeast Asia and Japanese waters. Many of these new species are found in

untouched and poorly investigated areas such as estuaries, benthopelagic zones, coral

reefs and marginal basins (Nishida and Nishikawa 2011).

Rhincodon typus and its Feeding Habits

Rhincodon typus, commonly called the whale shark, is the only representative

of the family Rhincodontidae and the current known largest extant fish species


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(Compagno 1984). The whale shark, together with the Basking Shark (Cetorhinus

maximus) and the Megamouth Shark (Megachasma pelagios), are considered to be the

only filter-feeding shark species relying solely on plankton and nekton as their food

source (Colman 1997). Whale sharks are distributed along tropical, sub-tropical and a

few recorded in warm temperate waters and are known to be highly migratory but

returns to same sites annually (Compagno 1984,Colman 1997).

Whale sharks are usually harmless to humans even though they are enormous

in size. The largest whale shark, found in Taiwan, reached a length of 20 meters and

weighed 34 tons (Chen and Phipps 2002). Since whale sharks are filter-feeders, their

food preferences include a variety of almost all suspended organisms in the ocean

such as zooplankton, nekton, and several small fish (Gudger 1941,Compagno 1984,

Colman 1997).

Whale sharks are usually found individually but sometimes they aggregate. In

Gladden Spit, Belize, about 25 whale sharks are found aggregating mainly feeding on

fresh spawn of cubera, Lutjanus cyanopterus, and dog snappers Lutjanus jocu

(Heyman et al. 2001). Recently, a newly discovered aggregation site of whale sharks

was found at Al Shaheen oil field, which is 90 kilometers off the coast of Qatar in the

Arabian Gulf. About 100 individuals were estimated within an area of 1 km2feeding

on surface zooplankton, consisting primarily of mackerel tuna (Euthynnus affinis)

eggs (Robinson et al. 2013).

The whale sharks are observed to exhibit two types of feeding behavior:

passive sub-surface ram-feeding and active surface feeding. Passive feeding involves

opening of the mouth while slowly swimming and filtering water in its path. Active

surface feeding on the other hand makes use of a suction filter-feeding mechanism.


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An active feeder sucks in and filters water while remaining still either horizontally or

vertically (Gudger 1941).

Rhincodon typus in the Philippines

In a study conducted by Eckert et al. (2002), using satellite telemetry, the

movements and distances travelled by individual whale sharks starting from the

greater Sulu Sea region were recorded. The rate of travel of the whale sharks observed

averages 24 km/day, a proof that sharks were highly mobile and did not seem to

remain in any particular area.

The Philippines is a tropical country making it a part of the whale sharks

migration route (Barut et al. 2003). Whale shark is commonly called butanding in

the Philippines. Whale shark sightings occurring singly or in groups nearshore and

offshore are recorded in many areas of the Philippines (Barut et al. 2003). Fishery

records show abundance of whale shark particularly around the Bohol and Sulu Seas

and southeastern Mindanao (Alava and Cantos 2004). Other places in the Philippines

where seasonal aggregation of whale sharks can be observed include Donsol,

Sorsogon, Honda Bay, Palawan, Zambales coasts (Alava and Cantos 2004), and

Sogod Bay, Southern Leyte (Bochove et al. 2007).

Sogod Bay, Southern Leyte

Sogod Bay can be found in the southernmost part of Southern Leyte, one of

the six provinces of Eastern Visayas.Some of the coral reefs in the Philippines that

remain to be the least disturbed and least researched are found in the waters of


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Southern Leyte. A large body of water in Southern Leyte, which is the Sogod Bay,

serves as an important fishing spot for fishermen living by the coastlines of the bay.

Sogod Bay is known to host a variety of reef fish and other commercially marketed

fish such as tuna, flying fish, herrings, anchovies, shellfish, and mackerel (Bochove et

al. 2007). The abundance of fish also means that the bay is a major breeding ground

of fishes where they spawn and reproduce making it an attractive food source for

large opportunistic forager organisms such as pilot whales, melon-headed whales,

dolphins, and whale sharks (Bochove et al. 2007). According to Mr. Ernesto Felicio

(pers. comm.), whale sharks were often found drifting along the Pintuyan point and

Son-ok point as long as he can remember.


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METHODOLOGY

Study Site

Three sampling stations were established along the southern part of Sogod

Bay, Southern Leyte. Sampling Station 1 is situated near the tip of Pintuyan (N 09

54 56.9, E 125 15 10.9), Station 2 is situated near Bennet Port of San Ricardo (N

09 54 53.69, E 125 17 32.7), and Station 3 is situated in deeper waters().

Physico-chemical Analysis

Physico-chemical parameters of the waters in each sampling station were

taken and recorded. These include current velocity, depth, light intensity, temperature,

salinity, dissolved oxygen, and pH. Velocity of the current was assessed with the use

of a fabricated drogue. The drogue was allowed to drift freely in the direction of the

current until it reached one meter. The time it took to reach one meter was recorded

and the direction of the current was estimated using a compass. Current was

calculated using the following formula:

Depth was measured using a calibrated rope. Light intensity was measured

with the use of EXTECH light meter. Temperature was measured with the use of a

centigrade field thermometer. Salinity was examined using a handheld Attago


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refractometer. Dissolved Oxygen, and the pH of the water was measured using a

EUTECH multiparameter.

Figure 1. Sampling Stations off Sogod Bay, Southern Leyte from August 2013 to

March 2014. Red dots indicate the sampling stations

Station 1

Station 2Station 3


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Collection and Preparation of Samples

Water samples at each station were collected once every sampling period in

the months of August and October of year 2013 and March 2014.

Qualitative Analysis

A conical plankton net extending up to one meter in length with a 30 cm

diameter and 20 m mesh size was used for obtaining water samples. The plankton

net was lowered one meter below the surface and then towed vertically. Water

collected was dispensed to a 100 mL pre-labeled plastic bottle then, ten milliliters of

formalin was added for preservation. Water samples were collected twice per station.

Quantitative Analysis

A 2.2L capacity WILDCO vertical sampler was lowered one meter below

water surface at each station followed by a messenger that triggered the trapping

mechanism of the sampler, sealing the water. Water collected was transferred to a pre-

labeled one liter plastic bottle. Ten milliliters of formalin was added for fixation and

preservation. Water samples were collected twice per station.

Preparation of Samples

The preserved one liter samples were stored undisturbed for 24 hours which

allowed settlement of the preserved and suspended plankton. After settling, a capillary

tube was placed carefully in the bottle which sucked out 800mL of supernatant. The

remaining 200mL of the sample was transferred into a 250mL graduated cylinder and

was stored again for 24 hours undisturbed. After settling, 150mL of supernatant was


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dispensed using the same suction technique. A concentrated final volume of

approximately 50mL of the sample was acquired and transferred into a 50mL amber

bottle.

Zooplankton Identification

One-milliliter of the 250mL sample for qualitative analysis was placed on a

glass slide. It is then viewed under a light compound microscope with 150x

magnification. Zooplankton samples were identified based on their structure and

morphology using the taxonomic keys of Yamaji (1984) and Larink and Westheide

(2006). Identification was conducted up to family or order level. Photomicrograph

softcopies of the zooplankton identified was verified by Mr. Joseph Dominic Palermo

from Marine Science Institute, University of the Philippines Diliman.

Cell Density Determination

One-milliliter of the 50mL concentrated sample was obtained for cell density

determination. The storage bottle was shaken first to even out the suspended

zooplankton in the sample then one-milliliter of aliquot was drawn out from the

bottle. The aliquot was dispensed on a Sedgwick-Rafter counting chamber and then

viewed under a light compound microscope. At least 300 cells were counted in the

sample. Cell density was determined using the following formula:


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Data Analyses

Diversity was estimated using Shannon-Wiener index:

Where:

H = the Shannon diversity index

Pi = fraction of the entire population madeup of species i

S = numbers of species encountered

= sum from species 1 to species


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RESULTS

Zooplankton Abundance and Composition

Quantitative Analysis

There were nineteen zooplankton groups encountered in the study. Copepod

nauplii were observed but grouped as one since each species from different orders

were morphologically indiscernible from one another under an ordinary light

microscope. All zooplankton groups were observed in the month of March 2014.

Families Phyllodocidae and Veneridae were absent in the month of October 2013

while families Atlantidae and Limacinidae were absent in the month of August 2013.

(See Table 1)

Copepod nauplius dominated the August and October 2013 sampling periods

with densities of 5.8x102 ind./L and 4.7x102ind./L respectively. By March 2014, all

stations were dominated by family Calanidae (1.1x103 ind./L) copepods. (See figure

2)

The highest total density (7.9x103 ind./L) was observed in Station 2 during

March 2014 sampling while the lowest (1.3x103 ind./L) was observed in October 2013

sampling (See figure 2). Accounting for all stations and comparing each month, the

highest mean total density was 7.7x103 ind./L in the month of March 2014 and the

lowest was 1.9x103 ind./L in the month of October 2013. (See figure 3)


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Table 1. Zooplankton groups observed off Sogod Bay, Southern Leyte. Orders Calanoida, Cyclopoida, Harpacticoida, andPoecilostomatoida are classified as copepods. Teleost eggs and ophiuroid larvae were not identified to family level due to

the lack of morphological features

Order Calanoida Cyclopoida Harpacticoida Poecilostomatoida Sessilia Oligotrichida

Family Calanidae Oithonidae Ectinosomatidae Oncaeidae Balanidae Rhabdonellidae

Paracalanidae Corycaeidae Tintinnidae

Codonellidae

Phylum Mollusca Annelida Chordata Echinodermata

Family Atlantidae Phyllodocidae Oikopleuridae Ophiuroidea (class)

Limacinidae Sabillaridae Teleost Eggs (not family)

Veneridae


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Figure 2. Zooplankton composition and density in Stations 1, 2 and 3 in the samplingmonths August and October 2013, and March 2014 off Sogod Bay, Southern

Leyte. The colored section of the bars refer to copepod zooplankton groupsand the shades of grey refer to non-copepod zooplankton groups

0 1 2 3 4 5 6 7 8

Station 1

Station 2

August

0 1 2 3 4 5 6 7 8

Station 1

Station 2

Station 3

October

0 1 2 3 4 5 6 7 8

Station 1

Station 2

Station3

density (x103ind./L)

March

Copepod Nauplius Calanidae Paracalanidae Oithonidae

Corycaeidae Ectinosomatidae Oncaeidae Balanidae

Rhabdonellidae Codonellidae Tintinnidae Ophiuroidea

Atlantidae Limacinidae Veneridae Phyllodocidae

Sabellaridae Oikopleuridae Teleost Egg


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Figure 3. Mean zooplankton abundance in the months of August and October 2013, andMarch 2014 off Sogod Bay, Southern Leyte. The colored section of the bars

refer to copepod zooplankton groups and the shades of grey refer to non-

copepod zooplankton groups

0

1

2

3

4

5

6

7

8

August October March

density

(x103ind.

/L)

Sampling Months

Teleost Egg

Oikopleuridae

Sabellaridae

Phyllodocidae

Veneridae

Limacinidae

Atlantidae

Ophiuroidea

Tintinnidae

Codonellidae

Rhabdonellidae

Balanidae

Oncaeidae

Ectinosomatidae

Corycaeidae

Oithonidae

Paracalanidae

Calanidae

Copepod Nauplius


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Figure 4. Actinotrocha larvae from Family Phoronidae of Phylum Phoronida in Station 2

during March 2014 sampling.

Qualitative Analysis

The same zooplankton groups observed in quantitative analysis were also

observed in the qualitative analysis. However, an additional zooplankton group

(Actinotrocha larvae from Family Phoronidae of Phylum Phoronida) was observed in the

sample from Station 2 in the March 2014 sampling.

Zooplankton Diversity

Diversity values for the three stations during the months of August and October

2013 and March 2014 is shown in figure 5. Station 2 during the March 2014 sampling

has the highest recorded diversity of H=2.56. On the other hand, Station 1 was the least

diverse station in October 2013 sampling with a diversity value of H=1.44.


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Figure 5. Zooplankton diversity (H) in Stations 1, 2, and 3 in the months of August and

October 2013, and March 2014 off Sogod Bay, Southern Leyte

Physico-chemical Parameters

Values of physico-chemical parameters determined per station are

summarized in Table 1. Depth ranged from 4.5 to 10 m in Stations 1 and 2. The deepest

sampling station was Station 3 with depths reaching approximately 15 m 27 m. Light

intensity values range from 1.77103

Fc to 7.51.103Fc. Temperature ranged from 28-

30.4 C with the highest temperature, 30.4C, recorded in Station 2 during March 2014

sampling and the lowest temperature, 28 C, recorded Station 1 during the month of

1.47

1.70

1.44

1.77

1.66

2.49

2.56

2.54

0 0.5 1 1.5 2 2.5 3

Station 1

Station 2

Station 1

Station 2

Station 3

Station 1

Station 2

Station 3

Shannon-Wiener Diversity Index (H')

March 2014

October 2013

August 2013


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October 2013. Values for pH measured varied from 7.9 - 8.53. Salinity was highest

during the month of March with the highest value of 38 ppt recorded in Station 3 while

values for the months of August 2013 and October 2013 ranged from 29 - 30. However,

dissolved oxygen during the month of August in Stations 1 and 2 were recorded with DO

values of 8.01 mg/L and 7.55 mg/L, respectively. DO was not measured for the sampling

months of October and March.


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Table 2. Summary of physico-chemical parameters during August (2013), October (2013) and March (2014) sampling in Sogod Bay,Southern Leyte, Philippines. (N.d. = no data)

Depth(m)

Light Intensity(Fc)

Temperature(C)

Salinity(ppt)

pHDissolved Oxygen

(mg/L)

August 6.5 3.931037.51.10

3 2930.3 3030.3 8.028.03 7.558.01

October 7- ~27 m 1.771035.310

3 2830 2935 7.9 - 8.02 N.d.

March 10-20 2.531036.4610

3 2930.4 3238 8.238.53 N.d.


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DISCUSSION

Zooplankton Abundance off Sogod Bay, Southern Leyte

Copepods, according to a review by (Kiorboe 2011)are successful due to their

predator escaping and prey capturing capabilities. Copepods are also efficient in

locating mate in the dilute community they thrive in (Kiorboe 2011). High abundance

of copepod nauplii throughout the whole sampling period can be attributed to the high

productivity of copepod species in the study site. As stated earlier, copepod nauplii

and other small zooplankton are mostly preyed upon by bigger omnivorous and

carnivorous zooplankton. Hence, contribution of copepod nauplii in the marine

community is ecologically significant. Figure 2 testifies the large contribution of

copepod nauplii in the zooplankton population in all sampling periods dominating the

sampling months of August and October 2013. In proportion, the contribution of

copepod nauplii in the population decreased during March 2014, showed in Figure 2,

due to the increased number of possible planktonic predators such as larger

zooplankters.

Figure 3 shows that the month of October 2013 had the least zooplankton

abundance and in contrary March 2014 had the greatest, up to three times more than

October 2013. A contemporary study conducted by Ida (2014) off Sogod Bay shows

the least and the greatest value of phytoplankton abundance and diversity in the same

months of October 2013 and March 2014 respectively. Zooplankton depend primarily

on phytoplankton as food source, the occurrence of abundant phytoplankton species

will therefore increase zooplankton abundance.


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As mentioned earlier, the month of March is included in the duration of whale

shark season off Sogod Bay from November to July. Increased zooplankton grazing

on phytoplankton might be a factor for the whale shark migration in the mentioned

bay. According to (Martin 2007), like the baleen whale and some procellariid birds,

the whale shark might also take the chemical released by phytoplankton when they

are grazed upon by zooplankton as a foraging cue.

Also, a notable observance is the significant inflation in harpacticoid

abundance (see Figure 2). The large increase in number of harpacticoid species

compared to other zooplankton in the month of March 2014 can be attributed to the

warm season during this month. Compared to August and October 2013 as shown in

Table 1, the month of March 2014 has the highest recorded temperature, salinity and

light intensity. According to (Uye et al. 2002), most harpacticoid species tend to

reproduce more during warm season because the duration time from egg laying to

adulthood best depends on higher temperature.

Diversity and Composition of Zooplankton Groups off Sogod Bay, Southern

Leyte

The increased diversity in the month of March 2014 can be attributed to the

increase in zooplankton abundance and composition. Additional zooplankton groups

were encountered in samples taken during the same month. These additional groups

include the free swimming larvae of Family Phoronidae Actinotroch, and Class

Ophiuroidea Pluteus. Adult forms of phoronids or horshoe worms and ophiuroids or

brittle stars are basically bottom dwelling organisms. Also an increase in teleost egg

density from 13 ind./L during October 2013 to 100 ind./L during March 2014 was


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observed. Though these zooplankton groups are not plentiful enough to be considered

as significant contributors to the total zooplankton population in the three stations,

occurrence of more meroplanktonic forms and increase in their diversity in the month

of March may suggest that this presence of a number of prey resources are part of the

whale sharks prey diet despite the fact that majority of what they consume are

holoplanktonic zooplankton (e.g. copepods) (Nelson and Eckert 2007).

However, krills or euphausiids, were not encountered in any of the stations in

the study site during the three sampling events. Krills are also one of the preferred

food of the whale shark. In some parts of Bohol Sea, Philippines, locals use krills and

mysis shrimp commonly called as alamang to hand feed and lure whale sharks

(Alava et al. 1997).

Zooplankton Abundance and Diversity per Sampling Station

In contrast to the other sampling stations, Station 2 was the nearest station to

the Bennet Port where there is better mixing of nutrients in the water. Nearby

residential structures are also observed which can be sources of additional nutrients to

run-offs. The same station was also observed to have the most abundant and diverse

zooplankton composition and phytoplankton (Ida 2014). This suggests that key

nutrients for some zooplankton are accessible in Station 2 but are either inaccessible

or absent in Stations 1 and 3. For instance, the actinotroch larva was only observed in

Station 2 during the March 2014 sampling because dinoflagellates were part of the

larvas diet (Strathmann and Bone 1997). A report by Bochove et al. (2007) and a

study by Labaja et al. (2013)account more sightings of whale shark near Station 2

which can be attributed to its zooplankton abundance.


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CONCLUSION

A total of 19 zooplankton groups were identified. The study site were

dominated by Copepods (66%) followed by Oligotrichida (15%) and then Polychaetes

(11%). High copepod nauplii abundance (16%) can be attributed to the high

productivity of copepods. March 2014, the sampling event during the whale shark

season, yielded the highest mean abundance (7.7x103 ind./L) of zooplankton. And

October 2013, during the off peak season, had the least (1.9x103ind./L) zooplankton

mean abundance. March 2014 also was the most diverse (H= 2.53) zooplankton

community compared to the first two sampling events.


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RECOMMENDATION

More sampling stations including the non-feeding grounds of whale is highly

recommended for comparative data. Additional depths for each station and longer

sampling duration are also essential to sample more zooplankton groups.

Identification up to genus or species level is also recommended.


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APPENDIX

Zooplankton Identified

Order Calanoida

Family Calanidae Family Paracalanidae

Order Cyclopoida

Family Corycaeidae Family Oithonidae


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Order Oligotrichida

Family Rhabdonellida Family Tintinnidae

Family Codonellidae

Phylum Mollusca

Class Gastropoda

Family Atlantidae Family Limacinidae


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Class Bivalvia

Family Veneridae

Phylum Tunicata

Class Appendicularia

Family Oikopleuridae

Phylum Annelida

Class Polychaeta

Family Sabellaridae Family Phyllodocidae


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Phylum Echinodermata

Class Ophiuroidea Pluteus Larvae

Teleost Eggs

Surface Zooplankton Sogod bay

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