Life cycle and population dynamics of the calanoid copepod Pseudocalanus spp. in the Baltic Sea and North Sea [Elektronische Ressource] / vorgelegt von Jasmin Renz

Jrenz

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2006
• Nombre de lectures: 10
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

Alfred-Wegener-Institut für Polar und Meeresforschung
Bremerhaven
Life cycle and population dynamics
of the calanoid copepod Pseudocalanus spp.
in the Baltic Sea and North Sea
DISSERTATION
zur
Erlangung des akademischen Grades
des Doktors der Naturwissenschaften
(Dr. rer. nat.)
am Fachbereich 2 (Biologie/Chemie) der
Universität Bremen
vorgelegt von
Jasmin Renz
Bremen, Juni 2006 1. Gutachter: Prof. Dr. Wilhelm Hagen, Universität Bremen
2. Gutachter: Prof. Dr. Sigrid Schiel, Alfred-Wegener-Institut Bremerhaven CONTENTS
SUMMARY III
ZUSAMMENFASSUNG V
1 INTRODUCTION 1
1.1 Distribution patterns of calanoid copepods 1
1.2 Life cycles of calanoid copepods in different geographical regions 2
1.3 Population dynamics of calanoid copepods 2
1.4 The genus Pseudocalanus 3
Pseudocalanus acuspes and Pseudocalanus elongatus 5
2 THESIS OUTLINE 8
3 MATERIAL AND METHODS 10
3.1 Study sites 10
3.1.1 Baltic Sea 10
3.1.2 North Sea 10
3.2 Sampling 11
3.3 Weighted mean depth (WMD) 13
3.4 Length measurement 13
3.5 Egg production 14
3.6 Moulting and growth rate 14
3.7 Secondary production and productivity 14
3.8 Statistics 14
4 DISCUSSION 16
4.1 The distribution of Pseudocalanus species in the Baltic and North Sea 16
4.1.1 Vertical distribution 18
4.2 Life cycle 19

I 4.3 Population dynamics 21
4.3.1 Reproduction 21
4.3.2 Development and growth 22
4.3.3 Secondary production 23
4.3.4 Mortality 23
4.4 Climate variability and Pseudocalanus spp. 25
5 CONCLUSIONS 28
6 PUBLICATIONS 29
PUBLICATION I 31
Renz J and Hirche H-J (2006) Life cycle of Pseudocalanus acuspes Giesbrecht
(Copepoda, Calanoida) in the Central Baltic Sea: I. Seasonal and spatial distribution.
Mar Biol 148: 567-580, DOI 10.1007/s00227-005-0103-5
PUBLICATION II 47
Renz J, Peters J, Hirche H-J (2006) Life cycle of Pseudocalanus acuspes Giesbrecht
(Copepoda, Calanoida) in the Central Baltic Sea: II. Reproduction, growth and
secondary production. Mar Biol submitted
PUBLICATION III 77
Peters J, Renz J, van Beusekom J, Boersma M, Hagen W (2006) Trophodynamics
and seasonal cycle of the copepod Pseudocalanus acuspes in the Central Baltic Sea
(Bornholm Basin) – evidence from lipid composition. Mar Biol DOI 10.1007/s00227-
006-0290-8
MANUSCRIPT 93
Renz J and Hirche H-J Life cycle and population dynamics of Pseudocalanus
elongatus Boeck in the southern North Sea. Manuscript
Further publications
Renz J, Peters J, Hirche H-J, Hagen W (2006) Does the calanoid copepod
Pseudocalanus acuspes retain an arctic life cycle in the Central Baltic Sea? GLOBEC
International Newsletter 12 (1): 71-73

Renz J, Hirche H-J (2004) Life cycle of Pseudocalanus acuspes in the Central Baltic
Sea. ICES CM L:20
7 REFERENCES 122
8 ACKNOWLEDGEMENTS 132
ABBREVIATIONS 133
II Summary
Summary
Calanoid copepods of the genus Pseudocalanus constitute important members of the
zooplankton in the northern hemisphere and play a major role in the recruitment and stock
dynamics of commercially used fish. This study analyses the population dynamics of the
calanoid copepod Pseudocalanus spp. in the Baltic and North Sea ecosystems and compares
life cycle characteristics, vital rates and secondary production of the two congener species, P.
acuspes from the Baltic Sea and P. elongatus from the North Sea. Reproduction, growth and
secondary production of these species are interpreted in the light of the nutritional environment
and hydrography. The connected continental shelf areas of the Baltic Sea and the North Sea
exhibit pronounced differences in their hydrographic conditions and number of species and
were the object of a comparative study in the framework of the GLOBEC Germany Project.
The study on the population dynamics of P. acuspes in the Bornholm Basin (central Baltic Sea)
was carried out on 17 cruises between March 2002 and July 2003. P. acuspes was an important
member of the zooplankton throughout the year, with maximum abundances up to 618*10³ and
-2
869*10³ n m in May 2002 and April 2003, respectively. Maximum biomass, estimated from
-2
prosome length, was 594 (May 2002) and 855 mg C m (May 2003). A stage specific
ontogenetic vertical distribution with youngest stages highest up in the water column and older
stages concentrated in deeper layers was governed by physiological requirements and
therefore closely related to hydrographic conditions. Copepodite stages V (CV) and adults were
distributed in the region of the permanent halocline located in approx. 60 m depth, where they
were subjected to higher salinities, while nauplii and younger stages preferred intermediate
waters. However, in particular of this high latitude species, all stages avoided the thermocline in
summer. The characteristical vertical distribution pattern exposed especially older stages to
their main predators, herring and sprat, which are known to feed in the region of the halocline.
All stages of P. acuspes were present year round, with a stage shift from nauplii in April/May to
CIV and CV in November indicating a slow seasonal development. This was confirmed by
extremely long stage durations of 15-25 days at 4°C in May and July 2003, determined from
moulting experiments. Maximum growth rates based on stage durations amounted to 0.03-0.05
-1
d in CI-CIV. The mean egg production rate (EPR) showed a seasonal course with highest
-1 -1 -1 -1
rates in April 2002 (3.6 eggs f d ) and 2003 (2.1 eggs f d ), corresponding to a mean specific
-1 -2
egg production rate (SEPR) of 0.13 and 0.04 d . Mean secondary production was 9.1 mg C m
-1 -2 -1
d (max. 16 mg C m d ), corresponding to a mean productivity of 0.031. Based on lipid
composition of CV and females, stage structure data and a slow seasonal development there
was evidence, that the life cycle of P. acuspes resembles those of high latitude species with a
reproductive peak in spring and a successive accumulation of overwintering copepodite stages
during summer. However, a potential interposition of minor generations might occur during
summer.
The population dynamics of P. elongatus were studied in the southern North Sea between
February 2004 and May 2005. Maximum abundance was in the range of P. acuspes from the
III Summary
-2
Baltic Sea and reached up to 564*10³ n m in June 2004. Spatial distribution showed highest
abundance of nauplii and youngest stages in the southern and central part of the study area,
while older stages and adults concentrated in the central and westerly part. Stage durations
derived from moulting experiments ranged from 1 d for CII in February up to 9.2 d for CV in
April, with highest stage durations generally observed at lowest temperatures. Weight specific
-1
growth rates were highest in youngest stages in April and August (0.31 d ), while growth rate of
-1
females peaked in February/March and May (0.12-0.13 d ). Maximum EPR of females reached
-1 -1 -1
9.1 eggs f d in April 2004, while SEPR was highest in June (0.13 d ). Mean secondary
-2 -2
production of P. elongatus was 19 mg C m (max. 110 mg C m ) in May and June,
-1
corresponding to a mean productivity of 0.15 d . At least 3 generations were identified in the
southern North Sea between February and October 2004, distinguished by changes in prosome
length of females.
The comparison of P. acuspes from the Baltic Sea and P. elongatus from the North Sea
revealed strong differences in the population dynamics of this morphologically similar congener
species. The highly stratified Baltic Sea makes high demands on the distribution of the glacial
relict P. acuspes, which is adapted to a life at high latitudes. To reach optimal temperature
conditions, a vertical distribution below the summer thermocline is compellent. This vertical
innidation prevents utilisation of food from the euphotic zone by this primarily herbivorous
species. The food limitation, the low salinity and the low temperatures in the Baltic Sea lead to
diminished growth rates of all stages of P. acuspes, which is indicated by the stage structure
and the slow development in May and July. Compared to that, the growth of P. elongatus
seemed to be unlimited by food particularly during spring and summer, which is indicated by
lower stage durations and higher growth rates and results in a higher max. secondary
production. These differences emphasise the importance of careful identification and studies of
key species for an understanding of their role in the marine ecosystem.
IV Zusammenfassung
Zusammenfassung
Calanoide Copepoden der Gattung Pseudocalanus stellen eine wichtige Gruppe des
Zooplanktons in der nördlichen Hemisphäre dar und spielen eine bedeutende Rolle in der
Rekrutierung und der Bestandsdynamik kommerziell genutzter Fische. Diese Arbeit analysiert
die Populationsdynamik des calanoiden Copepoden Pseudocalanus spp. in den Ökosystemen
Ost- und Nordsee und vergleicht Charakteristika in Lebenszyklus und -raten und
Sekundärproduktion der verwandten Arten P. acuspes aus der Ostsee und P. elongatus aus der
Nordsee. Die Parameter Reproduktion, Wachstum und Sekundärproduktion dieser Arten
werden auf dem Hinte