Spatio-temporal variability of larval abundance and settlement of Perna perna: differential delivery of mussels
- Porri, Francesca, McQuaid, Christopher D, Radloff, Sarah E
- Authors: Porri, Francesca , McQuaid, Christopher D , Radloff, Sarah E
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6877 , http://hdl.handle.net/10962/d1011625 , http://dx.doi.org/10.3354/meps315141
- Description: We examined larval availability and settlement of the intertidal mussel Perna perna simultaneously at different spatial and temporal scales using a nested design at 2 sites, 3 km apart on the south coast of South Africa. Each site had 3 locations (300 m apart) where 5 artificial settler collectors were placed about 20 cm apart. Collectors were replaced on temporal scales varying from fortnightly (for 16 mo) to daily (2 series of 15 to 20 d). Each intertidal location was paired with an inshore location (these too were 300 m apart) within 500 m of the shore, where larval availability was measured by 3 vertical plankton hauls collected on the same dates as for settler sampling. There was strong temporal variation in abundances of larvae and settlers, and no correlation (r always < 0.14) was found between the two. Larvae were abundant only at the start of sampling and rare for the rest of the study, while distinct peaks in settler numbers occurred later. No spatial effect was detected for larval availability, while there was strong spatial variation in settlement at the location level. These results indicate that, on scales of 100s of m to km, delivery of larvae from the nearshore water column onto the shore is strongly differential, with some locations consistently receiving more settlers than others. We conclude that, at these sites, the patchiness in settlement observed on scales of 100s of m depends on differential delivery, rather than differential offshore distribution of larvae. We suggest that differential delivery is due to the effect of nearshore bottom topography on local hydrodynamics.
- Full Text:
- Date Issued: 2006
- Authors: Porri, Francesca , McQuaid, Christopher D , Radloff, Sarah E
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6877 , http://hdl.handle.net/10962/d1011625 , http://dx.doi.org/10.3354/meps315141
- Description: We examined larval availability and settlement of the intertidal mussel Perna perna simultaneously at different spatial and temporal scales using a nested design at 2 sites, 3 km apart on the south coast of South Africa. Each site had 3 locations (300 m apart) where 5 artificial settler collectors were placed about 20 cm apart. Collectors were replaced on temporal scales varying from fortnightly (for 16 mo) to daily (2 series of 15 to 20 d). Each intertidal location was paired with an inshore location (these too were 300 m apart) within 500 m of the shore, where larval availability was measured by 3 vertical plankton hauls collected on the same dates as for settler sampling. There was strong temporal variation in abundances of larvae and settlers, and no correlation (r always < 0.14) was found between the two. Larvae were abundant only at the start of sampling and rare for the rest of the study, while distinct peaks in settler numbers occurred later. No spatial effect was detected for larval availability, while there was strong spatial variation in settlement at the location level. These results indicate that, on scales of 100s of m to km, delivery of larvae from the nearshore water column onto the shore is strongly differential, with some locations consistently receiving more settlers than others. We conclude that, at these sites, the patchiness in settlement observed on scales of 100s of m depends on differential delivery, rather than differential offshore distribution of larvae. We suggest that differential delivery is due to the effect of nearshore bottom topography on local hydrodynamics.
- Full Text:
- Date Issued: 2006
Temporal scales of variation in settlement and recruitment of the mussel Perna perna (Linnaeus, 1758)
- Porri, Francesca, McQuaid, Christopher D, Radloff, Sarah E
- Authors: Porri, Francesca , McQuaid, Christopher D , Radloff, Sarah E
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6963 , http://hdl.handle.net/10962/d1012026 , http://dx.doi.org/10.1016/j.jembe.2005.11.008
- Description: Population dynamics of many intertidal organisms are strongly affected by the abundance and distribution of larvae arriving on the shore. In particular, not only absolute numbers of settlers but also the degree of synchronisation of settlement can have a strong influence on whether density-dependent or density-independent processes shape adult shape populations. Temporal variation in rates of settlement and recruitment of the mussel Perna perna on the south coast of South Africa was investigated using a nested spatial design at different temporal scales. Variability in settlement at spring tides was examined at two temporal scales: lunar (to investigate the effect of state of the moon on settlement) and tidal (to investigate the influence of state of the tide on mussel settlement). Recruitment over neap tides was examined at one temporal scale, fortnight (to investigate the effect of date on mussel recruitment). Strong temporal variation was evident for both settlement and recruitment, but not at all time scales. Distinct peaks of settler/recruit abundance were observed during the lunar and neap tide studies. Recruitment intensity differed over the course of the year, and pulsing of recruitment was generally synchronised among locations. However, the strength of pulsing differed dramatically among locations, giving a significant interaction between fortnight and location. The finest temporal scale, investigated in the tidal study, did not reveal a significant effect of the state of the tide on settlement. The state of the moon (new or full) was not significant as a main factor (p = 0.052), although generally more settlers arrived on the shore during new moon. Phase of the moon appeared to have an effect on settler abundances, but only when and where densities were high.
- Full Text:
- Date Issued: 2006
- Authors: Porri, Francesca , McQuaid, Christopher D , Radloff, Sarah E
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6963 , http://hdl.handle.net/10962/d1012026 , http://dx.doi.org/10.1016/j.jembe.2005.11.008
- Description: Population dynamics of many intertidal organisms are strongly affected by the abundance and distribution of larvae arriving on the shore. In particular, not only absolute numbers of settlers but also the degree of synchronisation of settlement can have a strong influence on whether density-dependent or density-independent processes shape adult shape populations. Temporal variation in rates of settlement and recruitment of the mussel Perna perna on the south coast of South Africa was investigated using a nested spatial design at different temporal scales. Variability in settlement at spring tides was examined at two temporal scales: lunar (to investigate the effect of state of the moon on settlement) and tidal (to investigate the influence of state of the tide on mussel settlement). Recruitment over neap tides was examined at one temporal scale, fortnight (to investigate the effect of date on mussel recruitment). Strong temporal variation was evident for both settlement and recruitment, but not at all time scales. Distinct peaks of settler/recruit abundance were observed during the lunar and neap tide studies. Recruitment intensity differed over the course of the year, and pulsing of recruitment was generally synchronised among locations. However, the strength of pulsing differed dramatically among locations, giving a significant interaction between fortnight and location. The finest temporal scale, investigated in the tidal study, did not reveal a significant effect of the state of the tide on settlement. The state of the moon (new or full) was not significant as a main factor (p = 0.052), although generally more settlers arrived on the shore during new moon. Phase of the moon appeared to have an effect on settler abundances, but only when and where densities were high.
- Full Text:
- Date Issued: 2006
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