'fO
5 Spatial and Temporal DistributIon Pallerns
cornis, Lanicc cOl1chilega, PygosfJio elegan,I', Polydora ligni, Spio lI1artinel1sis and
further spionid polychaete larvae which could not be determined to species level.
The timing and the abundances varied over the years of observation, (Fig. 5.1.6).
Larvae of some species reached rather high numbers before the algal bloom,
e.g. M. papillicornis and larvae of spionids. These species could probably feed
sufficiently on the few algae present, bacteria and detritus. The appearance of
larvae of L. conchilcga showed a close temporal connection to algal blooms in
1994 and 1995.
With the exception of S. martinensis the larval density of all other polychaete
species was reduced in 1995. An explanation could be a nutrition limitation resulting from the lack of the spring bloom. The successful recruitment of
S. martinensis could be explained by the late spawning of this species, which enabled it to profit from the summer bloom of algae in 1995.
After the ice winter, numbers of larvae of L. conchilega and M. papillicornis
were severely reduced in 1996 (compare Chap. 5.3.6). Since the adults of both
species are sensitive to cold temperatures, the low numbers of larvae are probably
caused by the death of the adults. Other species, however, were not intluenced by
the cold temperatures, e.g. P. elegans and P. ligni. Their larvae reached record
numbers in 1996.
The meroplankton data of the three years showed a high variability. While bivalve larvae appeared probably corresponding with the time of algal blooms and
resulting from simultaneous spawning of several bivalve species, the occurrence of
the polychaete larvae varied during the study period. This results from different
reproduction strategies and the wide range of food spectrum of the larvae.
:::J
o
6 0 0 0 , - - - - - - - - - - - , 3 ' 1 0 7
1994
4000
2000
1995
g 4000
Q;
(\)
c: 2000
~
t96
4000 ' 1
~
2x10 8
•
/ \
2000
I \
1X10 8
o
)1
~ ~
,0,100
JaniFebiMar i A!);iMay Jun Jli AugiSepi Oct INov Dec
-Lanice-Iarvae - - alqal celis
20000
10000
7
, - - - - - - - - - - - - - , - 3 ' 1 0
1994
1995
I\.
/
V
\
\
7
2x10
20000
1996
10000
+-T:'7r.:-i~:_:__t'_,~__"t.:""'=~_=_+O'100 Jan Feb Mar Apr May Jun Jul Aug Sap Oct Nov Dec
-PvaosDio-larvae - - alqal celis
Fig.5.1.6 Abundances of larvae of Lal1ice col1cizilega, Pygospio e1egal7.\' and algal cells
« 30 flm) during the time of observation (please note the different scales). (Data from Niesel
I 'f'f7 and Boysen-Ennen unpublished data)
5 Spatial and Temporal DistributIon Pallerns
cornis, Lanicc cOl1chilega, PygosfJio elegan,I', Polydora ligni, Spio lI1artinel1sis and
further spionid polychaete larvae which could not be determined to species level.
The timing and the abundances varied over the years of observation, (Fig. 5.1.6).
Larvae of some species reached rather high numbers before the algal bloom,
e.g. M. papillicornis and larvae of spionids. These species could probably feed
sufficiently on the few algae present, bacteria and detritus. The appearance of
larvae of L. conchilcga showed a close temporal connection to algal blooms in
1994 and 1995.
With the exception of S. martinensis the larval density of all other polychaete
species was reduced in 1995. An explanation could be a nutrition limitation resulting from the lack of the spring bloom. The successful recruitment of
S. martinensis could be explained by the late spawning of this species, which enabled it to profit from the summer bloom of algae in 1995.
After the ice winter, numbers of larvae of L. conchilega and M. papillicornis
were severely reduced in 1996 (compare Chap. 5.3.6). Since the adults of both
species are sensitive to cold temperatures, the low numbers of larvae are probably
caused by the death of the adults. Other species, however, were not intluenced by
the cold temperatures, e.g. P. elegans and P. ligni. Their larvae reached record
numbers in 1996.
The meroplankton data of the three years showed a high variability. While bivalve larvae appeared probably corresponding with the time of algal blooms and
resulting from simultaneous spawning of several bivalve species, the occurrence of
the polychaete larvae varied during the study period. This results from different
reproduction strategies and the wide range of food spectrum of the larvae.
:::J
o
6 0 0 0 , - - - - - - - - - - - , 3 ' 1 0 7
1994
4000
2000
1995
g 4000
Q;
(\)
c: 2000
~
t96
4000 ' 1
~
2x10 8
•
/ \
2000
I \
1X10 8
o
)1
~ ~
,0,100
JaniFebiMar i A!);iMay Jun Jli AugiSepi Oct INov Dec
-Lanice-Iarvae - - alqal celis
20000
10000
7
, - - - - - - - - - - - - - , - 3 ' 1 0
1994
1995
I\.
/
V
\
\
7
2x10
20000
1996
10000
+-T:'7r.:-i~:_:__t'_,~__"t.:""'=~_=_+O'100 Jan Feb Mar Apr May Jun Jul Aug Sap Oct Nov Dec
-PvaosDio-larvae - - alqal celis
Fig.5.1.6 Abundances of larvae of Lal1ice col1cizilega, Pygospio e1egal7.\' and algal cells
« 30 flm) during the time of observation (please note the different scales). (Data from Niesel
I 'f'f7 and Boysen-Ennen unpublished data)