C Al
Resume:
Hydrobiologia (****) ***:*** ***
ZOOPLANKTON ECOLOGY
Zooplankton assemblages as indicators of seasonal changes
in water masses in the boundary waters between the East
China Sea and the Taiwan Strait
Shih-Hui Hsiao Samba Ka Tien-Hsi Fang
Jiang-Shiou Hwang
Published online: 3 March 2011
Springer Science+Business Media B.V. 2011
Abstract Hydrology and trophic relationships are indicating their association with the cold waters of
frequently reported for inducing changes in mesozoo- the East China Coastal Current. Appendicularians and
plankton communities. This study investigated the N. scintillans were mainly associated with the coastal
distribution and abundance of mesozooplankton in the waters of Taiwan; whereas C. sinicus was concen-
boundary waters between the East China Sea and trated in the offshore waters along the coast of
the Taiwan Strait. Samples were collected using a Mainland China. Chaetognaths, Temora turbinata,
NOR-PAC zooplankton net towed horizontally at a Acrocalanus spp., and radiolarians were dominant in
depth of 2 m, at eight stations along a transect, in autumn, showing their association with the warm
March (spring) and October (autumn) 2005. The waters of the Kuroshio Branch Current. Oncaea
abundance of mesozooplankton was signi cantly venusta was relatively abundant during both seasons.
higher during autumn than spring. Densities of many Our study shows that, in addition to the in uence of
groups (e.g., Noctiluca scintillans, pteropods, cope- seasonal changes in the water masses, the distribution
pods, mysids, euphausiids, and other larva) increased and composition of mesozooplankton are highly
in October. During both seasons, copepods repre- in uenced by trophic interactions between zooplank-
sented more than 50% of the total zooplankton ton taxa, in the boundary waters of the Taiwan Strait
abundance. Noctiluca scintillans, appendicularians, and the East China Sea.
and Calanus sinicus were dominant in spring,
Keywords Copepods Appendicularians
Noctiluca scintillans Hydrology Kuroshio Branch
Guest editors: J.-S. Hwang and K. Martens / Zooplankton Current East China Coastal Current
Behavior and Ecology
S.-H. Hsiao S. Ka J.-S. Hwang Introduction
Institute of Marine Biology, National Taiwan Ocean
University, Keelung 202, Taiwan
e-mail: *******@****.****.***.**
In marine ecosystems, mesozooplankton organisms
play an important role, as a link between the primary
S.-H. Hsiao T.-H. Fang
producers and higher consumers (Humes, 1994;
Department of Marine Environmental Informatics,
National Taiwan Ocean University, Keelung 202, Taiwan Naganuma, 1996). Mesozooplankton grazes on phy-
toplankton and are consumed by zooplanktivorous
S.-H. Hsiao
sh and other carnivorous organisms such as jelly sh.
Department of Science Education, National Taipei
In addition, mesozooplankton organisms are highly
University of Education, Taipei 106, Taiwan
123
318 Hydrobiologia (2011) 666:317 330
source of nutrients for the East China Sea (Chen
sensitive to environmental variations such as seasonal
et al., 1995, 1996; Lee et al., 2004), in uencing
changes in water masses, inducing seasonal succes-
biological productivity and sh catches (Wong et al.,
sions and uctuations in the abundance, and distri-
1991; Liu et al., 1992; Gong et al., 1995). The water
bution of various communities or species in aquatic
masses have high temperature and salinity in the
ecosystems (Uye et al., 2000; Tseng et al., 2008).
KBW and low temperature and salinity in the CCW,
Thus, several mesozooplankton organisms (copepods
due to the discharge of freshwater from a series of
or others groups) are commonly used as indicators for
rivers in Mainland China (Lee et al., 2004), and
water masses and oceanic currents (Grant, 1991;
intermediate temperature and salinity in the South
Hwang & Wong, 2005; Hwang et al., 2006; Tseng
China Sea Water (SCSW) (Chu, 1971). Although,
et al., 2008). Furthermore, in the context of climatic
these different oceanic waters have been proposed as
changes, drastic changes are anticipated in physical
the primary driving forces behind the enrichment of
parameters, such as temperature and salinity in many
marine biodiversity in Taiwan (Wong et al., 2000;
marine ecosystems (Chen & Folt, 2002). Thus,
Liu et al., 2003; Hwang et al. 2004a, b, c, 2006),
studying the seasonal dynamics of zooplankton and
the means by which it relates to variations in water seasonal changes in the relative in uence of these
masses could provide a deeper understanding of water masses may act as a contributing factor in the
marine ecosystems and help to ameliorate predictions temporal variations of marine organisms.
concerning such changes, in the local context as well The purpose of this study was to examine the
as the global. impact of changes in water masses in the boundary
The boundary waters between the Taiwan Strait waters of the Taiwan Strait and the East China Sea, as
and East China Sea are primarily in uenced by three they pertain to the composition and seasonal dynam-
currents: the East China Coastal Current (ECCC), the ics of the mesozooplankton; and to evaluate the group
Kuroshio Branch Current (KBC), and the South association among the taxa in relation to trophic
China Sea Surface Current (SCSSC) (Jan et al., interactions. Unlike the study of Hwang et al. (2006),
2002). The seasonal in uence of these currents is this present study was performed not only on
governed primarily by the monsoon system (Jan copepods, but also on other important mesozooplank-
et al., 2002; Liang et al., 2003; Tseng & Shen, 2003). ton taxa. This study represents an attempt to under-
During winter, the northeastern (NE) monsoon stand the main factors determining the distribution
induces a southward movement of the ECCC into and composition of the mesozooplankton in the study
the Taiwan Strait, while the KBC ows northward area.
along the west coast of Taiwan (Wang & Chern,
1988; Hu et al., 1999). However, the Kuroshio
Branch Water (KBW) which is blocked by ECCC Materials and methods
in the Changyun Ridge of the Penghu Channel covers
the entire eastern half of the Strait, while the China Samples were collected during two cruises in spring
Coastal Waters (CCWs) are con ned to the western (March, 2005) and in autumn (October, 2005) at eight
side (Liang et al., 2003; Hwang et al., 2006). During stations on a transect extending along the boundary
spring, the weakened NE monsoon leads to northward waters of the Taiwan Strait and the East China Sea
intrusion of the KBW into the Penghu Channel, (Fig. 1) aboard the R/V Ocean Research-II.
in uencing the northern part of the Taiwan Strait (Jan
et al., 2002; Hwang et al., 2006). During summer, the Environmental data
southwestern (SW) monsoon induces southward
movement of the SCSSC and KBC in the Taiwan Monthly averages for sea surface temperatures and
Strait; whereas in autumn, the beginning of the NE concentrations of chlorophyll a in seawater were
monsoon leads to the intrusion of the CCW in the collected from advanced very high resolution radi-
northwestern (NW) reaches. The in uence of the ometer (AVHRR) recordings in March and October
KBC into the Taiwan Strait is higher in the summer of 2005. At each station, temperature and salinity
than in winter. The subsurface Kuroshio waters in were simultaneously recorded using the on board
conjunction with the Yangtze River is the major SeaBird CTD instrument.
123
Hydrobiologia (2011) 666:317 330 319
Fig. 1 Schematic showing the Taiwan Strait circulation in waters between the Taiwan Strait and the East China Sea, in
a winter, b spring, c summer and d fall, after Jan et al. (2002); March and October 2005
and e location of our sampling stations (St) in the boundary
123
320 Hydrobiologia (2011) 666:317 330
Zooplankton sampling a are shown in Fig. 2. In March, temperatures showed
a highly marked gradient between the northern coast
Zooplankton samples were collected using a NOR-PAC of Taiwan and the coast of mainland China, decreas-
ing from 18 to 12 C. In October, the variation was not
net (diameter of 45 cm, mesh size of 333 lm). A ow
as high, with values ranging between 25 and 26 C.
meter (Hydro-Bios) was mounted at the center of the
mouth opening. The net was towed 2 m below the Concentrations of chlorophyll a ranged between 0.5
and 5.0 mg m-3, with the highest levels observed in
surface. Sampling time was approximately 100 min at a
vessel cruise speed of two knots. The samples of the waters off the coast of mainland China.
zooplankton were immediately preserved in 5 10% The TS diagram distinguishes two different water
buffered formalin seawater. At the laboratory, when masses in March (Fig. 3): waters with low tempera-
necessary, samples were split into subsamples using a ture and salinity (St7 and St8), and waters with high
Folsom splitter to count a maximum number of 500 temperature and salinity (St1 to St6). In October, only
individuals of dominant species. Rare taxa were counted a single water mass with elevated temperature, and
from the entire sample. All taxa were listed and their salinity similar to that of St1 to St6 of March was
abundances expressed in number of individuals per detected along the transect. The CTD vertical pro les
cubic meter (ind. m-3). Copepods were identi ed of temperature and salinity for each season are
following the methods of Chen & Zhang (1965), Chen presented in Fig. 4. In March, temperatures and
et al. (1974), and Huys & Boxshall (1991), whereas salinity decreased from the coastal waters of Taiwan
(St1, temperature 16.2 0.7 C, salinity 34.6 0.01)
others organisms were identi ed in accordance with the
studies of Mitsuo & Masaaki (1997). to the coastal waters of mainland China (St8,
temperature 10.4 0.7 C, salinity 31.1 1.0). In
Data analyses October, any gradient was observed in the tempera-
ture of the surface water along the transect. However,
Mann Whitney U test (non-parametric) and Spear- along the coast of Taiwan (St1 to St3) a marked
man correlation analyses were performed using SPSS vertical gradient was observed in the temperature,
13.0 for Windows to compare the taxa abundances with the lowest values measured below 60 m of depth.
between the two season and the taxa relationships, In October, the lowest salinity values were recorded in
respectively. the surface coastal waters all along the transect.
To reduce the elevated heteroscedasticity observed
in the original data on the abundance of species, a Zooplankton
transformation was generated using regression coef-
cients estimated by maximizing the log likelihood Mean mesozooplankton abundance increased signif-
icantly between March (132.9 114.9 ind. m-3) and
function (Box & Cox, 1964). Accordingly, the matrix
October (390.2 169.3 ind. m-3) (Table 1). The
of data related to the abundance of dominant
zooplankton taxa was used in conjunction with densities of dominant taxa comprising populations
Bray Curtis similarity indices following logarithmic such as Noctiluca scintillans, pteropods, copepods,
transformations log(X ? 1) using PRIMER 5 (Plym- amphipods, decapods, and chaetognaths increased
outh Routines in Multivariate Ecological Research) signi cantly between March and October (Mann
Whitney U test, P \ 0.05). Copepods dominated the
programme. Taxa characterizing each cluster were
further identi ed using the Indicator Value (IndVal) zooplankton population making up 60 and 58% of the
index proposed by Dufrene & Legendre (1997). mean abundance in March and October, respectively.
However, their proportion was lower in Sts 1 and 2
off the coast of Taiwan (Fig. 5). Depending on the
Results season, other holoplanktonic taxa, such as chaetog-
naths, appendicularians, N. scintillans, and radiolari-
Environmental data ans, made up a major proportion of the population.
Chaetognaths were observed in all stations, constitut-
Monthly average information derived from AVHRR ing 11 and 10% of the total mean abundance in
recordings of sea surface temperature and chlorophyll March and October, respectively. Appendicularians
123
Hydrobiologia (2011) 666:317 330 321
Fig. 2 Monthly average
sea surface chlorophyll
a and temperatures (SSTs)
derived from averaged
hourly recordings
(AVHRRs) in March 2005
and October 2005
28 March and October, respectively. Radiolarians con-
St5
St8 stituted 9% of the total mean abundance in October.
St7 St6
St3
St4
24 Copepods
St2
St1
Temperature ( C)
Altogether, 72 species of copepod were identi ed
20 during the two seasons. These belong to 32 genera: 46
calanoids, 3 cyclopoids, 2 harpacticoids, and 21
St2
poecilostomatoids (Table 2). Copepod diversity was
St3
St5
16
St6 St4 St1 high during both seasons (Fig. 5). The Shannon index
value decreased from the coastal waters of Taiwan (Sts
1 and 2) to those of mainland China in March. The
12 St7
highest diversity index was observed from St2 to St6 in
October. Oncaea venusta was present in all sample
St8
stations (100% of occurrence) both in March and
8
October. Calanus sinicus and Euchaeta rimana were
present at all sample stations in March, whereas
Salinity
Canthocalanus pauper, Undinula vulgaris, Subeucal-
Fig. 3 Temperature salinity diagram of the water masses anus subcrassus, and Temora turbinata were present at
along the transect in the boundary waters between the Taiwan all sample stations in October (Table 2). The most
Strait and the East China Sea, in March (solid curves) and in
abundant copepod species in decreasing order of mean
October (dotted curves)
density were C. sinicus (46%), E. concinna (13%),
constituted 10% of the total mean abundance in March O. venusta (8%), and E. rimana (5%) in March;
and Acrocalanus gracilis (19%), T. turbinata (18%),
(Fig. 5). Noctiluca scintillans accounted 6 and 8% on
A. gibber (11%), O. venusta (8%), Paracalanus parvus
the total mean abundance of the mesozooplankton in
123
322 Hydrobiologia (2011) 666:317 330
March
Temperature Salinity
34.5
17.5
20 34
16.5
33.5
15.5
40 33
32.5
14.5
60 32
13.5
31.5
80 12.5 31
30.5
11.5
100 30
10.5
29.5
120 9.5 29
October
Temperature Salinity
27.5
20 26.5
25.5 35
40 24.5
23.5
60 22.5 34.5
21.5
80 20.5
19.5 34
100 18.5
17.5
120 16.5 33.5
St1 St2 St3 St4 St5 St6 St7 St8
St1 St2 St3 St4 St5 St6 St7 St8
Fig. 4 Vertical and horizontal pro les of temperature and salinity along the transect in the boundary waters between Taiwan Strait
and East China Sea in March and October 2005
Hierarchical classi cation and identi cation
(7%), P. aculeatus (5%), E. concinna (5%), Can.
of dominant zooplankton taxa assemblages
pauper (4%), T. discaudata (4%), and S. subcrassus
(4%) in October (Table 2).
Cluster analysis of zooplankton taxa indicated six
The mean abundance of copepods was signi -
cantly higher in October (237.5 163.2 ind. m-3) principal groups (Fig. 7). The rst hierarchical level
than in March (88.5 98.6 ind. m-3). In March, the of the cluster analysis separated the coastal waters of
density of copepods was lower than 100 ind. m-3 at Taiwan (St1 and St2) in March assemblage (cluster
IA) from all the remaining stations in any season
all stations, except at St8 where a peak of 325.1 ind.
m-3 was reached (Fig. 5). In contrast, in October, (cluster IB). The second hierarchical level distin-
guished the assemblage of St3 to St8 in March
the density of copepods was higher than 100 ind.
m-3 at all sample stations with two peaks at St3 (cluster IIA) from other assemblages of St1 to St8 in
(368.0 ind. m-3) and St5 (588.2 ind. m-3) (Fig. 5). October (cluster IIB). The next hierarchical level
distinguished four different clusters, representing St1
The density of C. sinicus was signi cantly higher in
(IIIA), St2 (IIIB), St3 to St7 (IIIC), and St8 (IIID) in
March than in October, whereas most of the other
March; and St1 to St3 (IIIE) and St4 to St8 (IIIF) in
dominant copepods were signi cantly more abun-
October. Clusters IA, IIIA, and IIIB (St1 and St2
dant in October than in March (Fig. 6). However,
in March) were characterized by low temperature
the density of Paracandacia bispinosa, Par. trun-
(17.5 17.6 C), high salinity (34.3 34.6) surface
cata, E. concinna, E. rimana, and P. parvus did not
waters (0 10 m of depth), with the highest densities
vary signi cantly between March and October
of appendicularians (33 41% of total zooplankton
(Fig. 6).
123
Hydrobiologia (2011) 666:317 330 323
sampled stations in October) were characterized by
Table 1 Total zooplankton abundance (mean SD, in ind.
m-3), relative abundance and occurrence (in %) of the main warm waters (27.2), high salinity (33.9 34.2), and the
groups found along the transect, in the boundary waters
highest densities of chaetognaths (8 10%), T. turbi-
between the Taiwan Strait and the East China Sea, during
nata (12 17%), A. gracilis (7 13%), A. gibber
March and October 2005
(5 8%), N. scintillans (7 13%), and radiolarians
Taxa March October
(9 22%) (Table 3).
Mean SD Occ. Mean SD Occ.
Total 132.9 114.9 390.2 169.3
Discussion
zooplankton
Noctiluca 6.0 11.5 63 7.6 5.5 100
In March (end of winter), a high-temperature gradient
scintillans
in the water and salinity along the transect between
Radiolaria 0.5 0.8 38 8.9 15.9 63
the coasts of Taiwan and mainland China showed
Foraminifera 0.0 0 0.5 0.9 25
differences between the two water masses, corre-
Medusa 5.1 4.5 88 1.6 1.0 100
sponding to waters associated with the ECCC (St7
Pteropoda 0.2 0.6 25 1.9 2.6 88
and St8, low salinity and temperature), and waters
Polychaeta 0.1 0.1 25 0.3 0.5 38
associated with the KBC (St1 to St6, high temper-
Bivalve molluscs 0.2 0.4 25 0.0 0
ature and salinity). In October (autumn), the water
larva
mass at all stations of the transect were characterized
\0.1 0.1
Cladocera 13 0.0 0
by high temperature and salinity, corresponding to
Ostracoda 1.2 1.1 75 2.1 3.4 63
the waters of KBC. Our results correspond with the
Copepoda 59.5 20.6 100 57.7 14.9 100
studies of Lan et al. (2004) and Hwang et al. (2006),
Cirripedia 0.1 0.3 13 0.1 0.2 13
which reported that during the spring, the water
Mysidacea 0.4 0.9 25 0.5 0.8 38
masses of the eastern side of the northern Taiwan
\0.1 \0.1
Amphipoda 13 2.3 3.6 75
Strait are in uenced mainly by the KBC, while the
Euphausiacea 0.2 0.4 25 0.8 1.2 50
western side is in uenced by the ECCC. In addition,
Decapoda 0.4 0.5 50 4.3 2.7 100
it was reported that the KBC introduced water masses
Heteropoda 0.0 0 0.0 0.1 13
with higher temperatures and salinity; whereas the
Chaetognatha 11.4 12.2 100 9.8 6.7 100
ECCC was associated with lower temperatures and
Echinodermata 1.1 1.7 50 0.2 0.5 13
salinity (Hsieh et al., 2004; Li et al., 2006).
larva
Our results illustrate the considerable impact of
Appendicularia 9.9 16.8 63 0.2 0.3 50
seasonal variations in water masses on the diversity,
Others (larva) 0.4 0.5 38 1.2 1.1 63
composition, and abundance of mesozooplankton.
Fish eggs 3.0 2.8 75 0.1 0.1 38
Between March and October, the abundance of the
most important taxa increased signi cantly with
abundance, indicator species with IndVal [25%) and changes in water mass. This change in the water
N. scintillans (12 32% of total zooplankton abun- mass was accompanied by an increase in temperature,
dance, indicator species for IIIA with IndVal [25%) suggesting that this last parameter is a major factor
(Table 3). Clusters IIA, IIIC, and IIID (St3 to St8 in in uencing seasonal changes in the community of
March) were characterized by the lowest temperature mesozooplankton. Previously, Hsieh & Chiu (2002)
(9.9 15.5 C) and salinity (29.7 33.4) surface waters reported that the abundance of copepods was posi-
(0 10 m of depth), with high densities of C. sinicus tively related to water temperature in the northern
(33 41% of total zooplankton abundance, indicator Taiwan Strait. This observation was reinforced by a
species with IndVal [25%) and chaetognaths (7 17% reduction in the abundance of copepods observed in
of total zooplankton abundance) (Table 3). Medusae the northwest of the Japan Sea during the winter
and E. concinna were also abundant at these stations (Dolganova & Zuenko, 2004). The dominance of
contributing 5 7% and 6 13% of total zooplankton copepods in mesozooplankton is commonly observed
abundance, respectively (Table 3). The remaining in marine ecosystems (Rakhesh et al., 2006; Eskinazi-
clusters (IIB, IIIE, and IIIF corresponding to the
Sant Anna & Bjornberg, 2006; Tse et al., 2007).
123
324 Hydrobiologia (2011) 666:317 330
Fig. 5 Station wise March October
variations in abundance 150 300 Noctiluca scintillans
dominant zooplankters and Radiolarians
Chaetognatha
diversity of copepods along 250 Appendicularians
120
Density (ind. m-3)
Density (ind. m-3)
Decapods
the transect in the boundary
Other groups
200
waters between the Taiwan 90
Strait and the East China
150
Sea, in March and October
60
2005. Note: the scales for 100
Y-axis for zooplankton
30
density in October differ by 50
factor 2 March
0 0
350 4.5 700 4.5
Copepods
Shannon index
4.0 4.0
300 600
3.5 3.5
Density (ind. m-3)
Density (ind. m-3)
Shannon index
250 500
Shannon index
3.0 3.0
200 400
2.5 2.5
150 300
2.0 2.0
100 200
1.5 1.5
50 100
1.0 1.0
0 0.5 0 0.5
St1 St2 St3 St4 St5 St6 St7 St8 St1 St2 St3 St4 St5 St6 St7 St8
Stations Stations
Many studies have reported the importance of This study basically noted that copepods are less
environmental factors (salinity, temperature, and abundant in the coastal waters of Taiwan (St1 and
primary production) on the abundance and distribu- St2) characterized by the highest abundances of
tion of zooplankton (e.g., Tan et al., 2004; Reese N. scintillans and appendicularians. Many studies
et al., 2005; Champalbert et al., 2007). In Dabob Bay have reported the predation of copepod eggs by
(Washington), Fulmer & Bollens (2005) reported that Noctiluca spp. (Daan, 1987; Quevedo et al., 1999).
chaetognaths, which are highly abundant in summer On the other hand, it has also been reported that
and spring, consume mostly copepods, thus their calanoid copepods are capable of ingesting appendi-
abundance is correlated to that of copepodites. Thus, cularians (Lopez-Urrutia et al., 2004; Stibor et al.,
in the present study, an increase in the abundance of 2004), which can explain the low densities of this
many predator groups such as chaetognaths may also taxa in offshore waters and the coastal waters of
be linked to an increase in the abundance of copepods Mainland China. Thus, predation of appendicularians
in autumn (Spearman correlation, q = 0.002). On the by copepods and the predation of copepod eggs by N.
other hand, in the coastal waters of Gulf of Maine scintillans (Spearman, signi cant negative correla-
(North America), Sherman & Shaner (1968) reported tion values with most of the dominant copepods)
high density of Saggita elegans (stage 1) resulting could explain the reverse distribution of copepods
from breeding in summer and autumn. This can and these other two taxa along the transect. The
support also the highest density of chaetognaths we present study shows that appendicularians and N.
observed in our study during autumn. Tse et al. scintillans are associated mainly with the coastal
(2007) reported that the currents from the South waters of Taiwan (St1 and St2) in March, a period for
China Sea carry various species of chaetognaths into which they could act as good indicators (IndVal
[25%). N. scintillans is particularly known for its
the coastal waters of Hong Kong. This phenomenon
may also be applicable to the KBC, owing from the association with coastal waters (Ka & Hwang, 2011)
southern side of Taiwan. However, the suggested and upwelling areas (Dela-Cruz et al., 2008).
hypothesis about reproduction may be an interesting Basically, our results show a higher degree of
one. species diversity at the stations in uenced by the
123
Hydrobiologia (2011) 666:317 330 325
Table 2 List and occurrence of the copepods species in the boundary waters between the Taiwan Strait and East China Sea in
March and October 2005
Taxa/species Taxa/species Taxa/species Taxa/species
Calanoida Clausocalanus farrani (25, 0) Delius nudus (0, 25) Corycaeidae
Paracalanus aculeatus
Acartiidae Clau. furcatus (38, 0) Corycaeus (Agetus) limbatus
(38, 88) (13, 38)
P. parvus (75, 50)
Acartia danae (0, 13) Clau. lividus (38, 0) C. (Agetus) typicus (13, 13)
A. erythraea (0, 13) Clau. mastigophorus (38, 25) Parvocalanus crassirostris C. (Corycaeus)
(0, 13) crassiusculus (50, 13)
A. paci ca (25, 0) Clau. minor (38, 0) Pontellidae C. (Corycaeus) speciosus (50, 63)
Calanidae Eucalanidae Calanopia minor (38, 0) C. (Ditrichocorycaeus)
andrewsi (38, 13)
Calanoides carinatus Rhincalanus Scolecithricidae C. (Ditrichocorycaeus) asiaticus
(13, 13) rostrifrons (25, 0) (38, 38)
Calanus sinicus (100, 38) Subeucalanus Scolecithricella minor C. (Ditrichocorycaeus) dahli
crassus (0, 50) (50, 38) (38, 13)
Canthocalanus pauper S. mucronatus (0, 25) Scolecithrix bradyi (13, 13) C. (Ditrichocorycaeus)
(75, 100) erythraeus (0, 13)
S. subcrassus (75, 100)
Cosmocalanus darwini Temoridae C. (Onychocorycaeus)
(63, 63) agilis (38, 13)
Temora discaudata (25, 75)
Nannocalanus minor (38, 63) Euchaetidae C. (Onychocorycaeus) catus (0, 63)
Undinula vulgaris (38, 100) Euchaeta concinna (88, 75) T. turbinata (88, 100) C. (Onychocorycaeus)
giesbrechti (25, 0)
Calocalanus gracilis (25, 0) E. indica (75, 50) Farranula carinata (0, 25)
Cal. pavo (38, 0) E. longicornis (25, 25) Cyclopoida F. gibbula (25, 63)
E. rimana (100, 88)
Candaciidae Oithonidae Unidenti ed species (0, 25)
Candacia ethiopica (50, 0) Lucicutiidae Oithona plumifera (25, 0) Oncaeidae
Paracandacia bispinosa Lucicutia avicornis (38, 0) O. rigida (38, 0) Oncaea clevei (0, 13)
(25, 38)
Par. simplex (0, 38) Metridinidae O. setigera (38, 38) O. conifera (0, 13)
Par. truncata (38, 38) Pleuromamma abdominalis Harpacticoida O. media (13, 25)
(13, 0)
Centropagidae P. gracilis (25, 13) Ectinosomatidae O. mediterranea (38, 50)
Centropages calaninus Paracalanidae Microsetella norvegica O. minuta (25, 25)
(0, 25) (13, 0)
O. venusta (100, 100)
Cen. furcatus (0, 63) Acrocalanus gibber (38, 88) Miraciidae
Cen. tenuiremis (90, 13) A. gracilis (88, 88) Macrosetella gracilis Sapphirinidae
(25, 13)
Clausocalanidae A. monachus (38, 0) Poecilostomatoida Sapphirina stellata (0, 13)
Bold characters represent the most abundant species; and numbers in brackets the occurrence of species in March and October,
respectively
KBC (Fig. 5). These ndings correspond to those of zooplankton differed among water masses in the
reported in previous studies (e.g., Shih & Chiu, 1998; boundary waters between the Taiwan Strait and the
Hsieh et al., 2004; Lan et al., 2004). Hsieh et al. East China Sea. In fact, we observed a shift in
(2004) have suggested that this is a result of the more the composition of species between March and
stable environment of the Kuroshio waters. However, October. C. sinicus and E. concinna were largely
in our study the lowest diversity observed in March the dominant species in March, whereas A. gracilis,
was caused primarily by the high abundance of A. gibber, T. turbinata, and O. venusta co-dominated
C. sinicus during the same period. The composition in October. The number of copepod species found in
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326 Hydrobiologia (2011) 666:317 330
Fig. 6 Variations in the 100
most abundant copepod
species (mean SE) along
Log abundance (ind. m )
ns ns
the transect in the boundary ns
-3
*** *** ns
waters between the Taiwan 10
Strait and the East China
Sea in March and October
2005 (Mann Whitney
U test, sig. ***P \ 0.001, 1
**P \ 0.01, *P \ 0.05, ns
P [ 0.05)
0.1
0.01
C. sinicus Cant. U. vulgaris E. rimana
Par. Par. S. E.
pauper bispinosa truncata subcrassus concinna
100
March
October
ns
Log abundance (ind. m )
*
-3
10
1
0.1
0.01
O. venusta
P. P. T. T.
A. gibber A. gracilis
aculeatus parvus discaudata turbinata
Fig. 7 Dendrogram
showing similarities in the
most abundant zooplankton
taxa in the boundary waters
between the Taiwan Strait
and the East China Sea in
March and October 2005,
based on the Bray Curtis
index
123
Hydrobiologia (2011) 666:317 330 327
Table 3 Dominant species, contributing [50% to the relative abundance of each cluster during the two sampling seasons, calculated
using Bray Curtis cluster analysis (see Fig. 7)
Dominant taxa Cluster level
Group Group Group Group Group Group Group Group Group Group
IA IB IIA IIB IIIA IIIB IIIC IIID IIIE IIIF
Noctiluca scintillans 22 4 7 12 13
32
Radiolarians 5 9 22
Medusae 7 7 5
Decapods 5
Chaetognaths **-**-**-**-*-*-**
Appendicularians 37 41 33
Fish eggs 5 7
Calanus sinicus 5 17 7
40 33 72
Acrocalanus gibber 6 8 5
Acr. gracilis 5 9 13 7
Paracalanus aculeatus 9
P. parvus 6
Euchaeta concinna 6 11 13
Temora turbinata 7 12 17
Oncaea venusta 5 7
Cumulative contribution **-**-**-**-**-** 70 84 72 51
Bold values represent indicator taxa with a IndVal [ 25%
presence of this copepod in warmer waters of 27.2 C
our study was lower than that of Hwang et al. (2006).
This can be explained by the fact that the study by (Lan et al., 2004). In autumn, C. sinicus is still the
Hwang et al. (2006) was performed over a longer most abundant of the large copepod species in the
period (5 years), covering more stations in the coastal Yellow Sea and East China Sea (Zuo et al., 2006).
waters of Taiwan and in the vicinity of the Danshui However, Zhang et al. (2007) reported that higher
estuary, which introduced typical estuarine copepod temperatures have a deleterious effect on both the
species such as Pseudodiaptomus annandalei. fecundity and hatching of C. sinicus, which could
A high degree of correlation between water masses explain the low abundance of this copepod in the
and the assemblage and distribution zooplankton was boundary waters of the Taiwan Strait and the East
recorded in our study, and in previous studies (Hsieh China Sea in autumn, in this study. However, in our
et al., 2004; Hwang et al., 2006; Zuo et al., 2006; Lan study, C. sinicus was present in very low densities
(0.1 0.3 ind. m-3) in autumn only from St6 to St7
et al., 2009). C. sinicus is known for its preference of
cold water masses (Uye, 1988; Lan et al., 2004; located near the coast of Mainland China, where
surface temperatures were lower (26.8 C) during this
Hwang et al., 2006), explaining the introduction of
this species to the Taiwan Strait from the East China period. This means that during autumn, the main
Sea, Yellow Sea, and Bohai Sea by the ECCC during population of C. sinicus is distributed on the northern
the NE monsoon in winter and spring (Zheng et al., side of the boundary waters between the Taiwan
1992; Hwang & Wong, 2005). Our study con rms Strait and the East China Sea. The other copepod
that C. sinicus is a good indicator of the intrusion of species present along our entire transect in October
waters into the Taiwan Strait from the East China Sea and along the western part during winter are domi-
in winter, as suggested by several other studies (e.g., nant in the South China Sea (Lo et al., 2001; Dur
Hwang & Wong, 2005; Hwang et al., 2006; Dur et al., 2007; Hwang et al., 2007). Euchaeta concinna,
et al., 2007). Recently, studies have reported the P. aculeatus, and A. gracilis, are the most abundant
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328 Hydrobiologia (2011) 666:317 330
communities and hydrology in the Senegal River Estuary.
species among those observed in this study during
Estuarine Coastal and Shelf Science 74: 381 394.
autumn, and have been associated with the Kuroshio
Chen, C.-Y. & C. L. Folt, 2002. Ecophysiological responses to
waters of northern Taiwan (Hsieh et al., 2004; Zuo warming events by two sympatric zooplankton species.
et al., 2006; Lan et al., 2009; Lee et al., 2009).
Contact this candidate