Brief description
A number of marine organisms do not provide any resources for their offspring other than the initial investment in larva. The extent of larval provisioning can be a strong determinant of larval fitness. Considerable variation in larval provisioning has been demonstrated but the factors responsible for this variation are not well understood. This dataset assesses if larval provisioning in the encrusting bryozoan Watersipora subtorquata is influenced by i) colony size, ii) colony age or iii) physical damage. To determine if these response vary with site conditions studies were undertaken at two locations within Port Phillip Bay, Victoria; Workshops Jetty, Williamstown and St Kilda pier, between September 2006 and March 2007.Lineage
Maintenance and Update Frequency: notPlanned
Statement: Establishment
Colonies were established on roughened Perspex plates attached to a backing panel suspended ~ 1.5 m below the low water level at both field sites. To minimise algal growth and sedimentation on the assemblages the panels were positioned so that the developing colonies faced the sediment. Twenty eight panels were deployed at Williamstown, and 11 at St Kilda; each panel contained 16 plates. Within 2 to 5 days Watersipora colonies were established and their location was marked on the plates. Sessile invertebrates other than Watersipora were removed from the plates. The abundance of Watersipora colonies was also controlled to prevent overcrowding.
Spawning larvae
Plates retrieved from the field were placed in dark aquaria for > 36 hours and then exposed to bright fluorescent light for up to five hours until all larvae had been released. Released larvae were stored in 10 % formalin.
Larval provisioning
The released larvae for each colony were counted and the length, width and height of larvae were measured under a microscope at 40 x magnification. When high numbers of larvae were released, 45 were randomly selected for measurement. The geometric mean of larval length, width and height was calculated as an index of larval size. Larval provisioning was assessed from counts of released larvae (N) and the mean and standard deviation (s) in larval size within a brood.
Colony area
Colony area was determined from photographic images (Olympus C50501 digital camera) using the image analysis program Image J v1.37 (Rasband).
Statement: Dataset:
This dataset assesses if larval provisioning in Watersipora subtorquata is influenced by i) colony size, ii) colony age or iii) physical damage. To determine if responses vary with site conditions studies were carried at two locations within Port Phillip Bay, Victoria; Workshops Jetty, Williamstown and St Kilda pier between September 2006 and March 2007
Effect of colony size:
Colonies were established fortnightly between the 11th Sept and 4th Dec 2006 at both sites. Once colonies were 10 weeks old they were collected from the field and spawned. Colony area was measured after spawning from photographic images (Olympus C50501 digital camera) using the image analysis program Image J v1.37 (Rasband).
Effects of colony age:
Changes in larval provisioning over time were examined in colonies of the same age established at Williamstown and St Kilda. All colonies were spawned at 10 weeks in the laboratory, but due to low numbers of larvae released in the first round, all were brought back to the laboratory again at 12 weeks and were spawned again. Eight plates from each site were selected randomly at 14, 16, 18 and 20 weeks after settlement. Since there were generally more than 1 colony per plate, more than 8 colonies were sampled per fortnight. Due to the number of replicates some plates were sampled more than once. At 22 weeks, all remaining colonies were spawned.
Effects of development in individual colonies:
Larval provisioning was assessed in colonies of the same age at 10 and 22 weeks post settlement; colonies were deployed at St Kilda. In addition a further group of colonies ~ 12 months old from Williamstown were spawned monthly.
Site effects (Reciprocal transplant):
To differentiate between phenological and site effects, colonies were established at St Kilda and Williamstown for two weeks. A subset of these colonies were either: i) transferred between sites, ii) left untouched or iii) transferred to the laboratory temporarily and then returned to their original location.
Physical damage:
A subset of colonies established at St Kilda were subject to various forms of physical damage at 10 weeks of age following spawning. In all the damage treatments 50% of the colony was removed from different regions of the colony. Damage treatments were: i) control - colonies left intact, ii) Halved - colony divided in two and half the colony removed iii) Outer - 50% of the outer perimeter of the colony was removed, leaving the older inner portion intact, iv) Inner - 50 % of the colony was removed from the centre of the colony leaving the younger zooids in the perimeter.
The data columns in the dataset are:
Time - weeks from the start of the study, Cohort - group of colonies that were settled at the same time, Age - age of colony in weeks at time of sampling, Site - Williamstown or St Kilda, Panel - panel number, Treatment - type of treatment (s=small plate, l=large plates, t=colonies followed over time), Damage - type of physical damage applied (control, undamaged colony, halved, inner or outer).
Response variables in dataset:
WCA = whole colony area (mm2); Perimeter (mm); Diameter (mm); ONA = area (mm2) of overgrown or necrotic tissue; LCA = live colony area (WCA-ONA); %LCA = (LCA/WCA* 100);
For more details on the methods and experimental design see Ryan, G (2007). Variation in maternal provisioning in Watersipora subtorquata. Honours Thesis, Department of Zoology, University of Melbourne.
Notes
PurposeTo assess the factors influencing variation in larval provisioning in the encrusting bryozoan Watersipora subtorquata.
Created: 06 06 2007
Data time period: 2006-09-01 to 2007-03-30
text: westlimit=144.90836; southlimit=-37.86467; eastlimit=144.96628; northlimit=-37.86089
text: uplimit=7; downlimit=2
Subjects
20 432002 |
BIOSPHERE |
Biosphere | Ecological Dynamics | Life History |
EARTH SCIENCE |
ECOLOGICAL DYNAMICS |
Oceans | Marine Biology | Marine Invertebrates |
Population Dynamics |
SPECIES/POPULATION INTERACTIONS |
St Kilda Pier, Melbourne, VIC |
Watersipora subtorquata |
Workshops Jetty, Williamstown, Melbourne VIC |
age |
area |
biota |
bryozoan |
colonies_settled |
damage |
diameter |
experimental_treatment |
larvae |
larvae provisioning |
panel_number |
perimeter |
physical_damage |
site |
time |
variability |
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Identifiers
- global : 45c7fdf0-13c2-11dc-b213-00188b4c0af8
