Macroalgae contribute to the diet of Patella vulgata from contrasting conditions of latitude and wave exposure in the UK

Analysis of gut contents and stable isotope composition of intertidal limpets (Patella vulgata) showed a major contribution of macroalgae to their diet, along with microalgae and invertebrates. Specimens were collected in areas with limited access to attached macroalgae, suggesting a major dietary component of drift algae. Gut contents of 480 animals from 2 moderately wave-exposed and 2 sheltered rocky shores in each of 2 regions (western Scotland, 55-56°N; and southwest England, 50°N), were analysed in 2 years (n = 30 site-1 yr-1). The abundance of microalgae, macroalgae and invertebrates within the guts was quantified using categorical abundance scales. Gut content composition was compared among regions and wave exposure conditions, showing that the diet of P. vulgata changes with both wave exposure and latitude. Microalgae were most abundant in limpet gut contents in animals from southwestern sites, whilst leathery/corticated macroalgae were more prevalent and abundant in limpets from sheltered and northern sites. P. vulgata appears to have a more flexible diet than previously appreciated, and these keystone grazers consume not only microalgae, but also large quantities of macroalgae and small invertebrates. To date, limpet grazing studies have focussed on their role in controlling recruitment of macroalgae by feeding on microscopic propagules and germlings. Consumption of adult algae suggests that P. vulgata may also directly control the biomass of attached macroalgae on the shore, whilst consumption of drift algae indicates that the species may play important roles in coupling subtidal and intertidal production.

Macroalgae contribute to the diet of Patella vulgata from contrasting conditions of latitude and wave exposure in the UK

Analysis of gut contents and stable isotope composition of intertidal limpets (Patella vulgata) showed a major contribution of macroalgae to their diet, along with microalgae and invertebrates. Specimens were collected in areas with limited access to attached macroalgae, suggesting a major dietary component of drift algae. Gut contents of 480 animals from 2 moderately wave-exposed and 2 sheltered rocky shores in each of 2 regions (western Scotland, 55-56°N; and southwest England, 50°N), were analysed in 2 years (n = 30 site-1 yr-1). The abundance of microalgae, macroalgae and invertebrates within the guts was quantified using categorical abundance scales. Gut content composition was compared among regions and wave exposure conditions, showing that the diet of P. vulgata changes with both wave exposure and latitude. Microalgae were most abundant in limpet gut contents in animals from southwestern sites, whilst leathery/corticated macroalgae were more prevalent and abundant in limpets from sheltered and northern sites. P. vulgata appears to have a more flexible diet than previously appreciated, and these keystone grazers consume not only microalgae, but also large quantities of macroalgae and small invertebrates. To date, limpet grazing studies have focussed on their role in controlling recruitment of macroalgae by feeding on microscopic propagules and germlings. Consumption of adult algae suggests that P. vulgata may also directly control the biomass of attached macroalgae on the shore, whilst consumption of drift algae indicates that the species may play important roles in coupling subtidal and intertidal production.

Chemotaxonomic phytoplankton patterns on the eastern boundary of the Atlantic Ocean

Surface pigment data from a transect along the eastern boundary of the Atlantic Ocean was analysed using CHEMTAX to yield more detailed information on the composition of phytoplankton communities. Total chlorophyll a concentrations varied from 0.03 mg m(-3) in a northern oligotrophic region to 30.3 mg m(-3) in the Benguela ecosystem. Diatoms dominated the Benguela, while both diatoms and haptophytes were the major groups in the Canary ecosystem and the temperate NE Atlantic. Prochlorococcus was the most prominent group in the southern oligotrophic region (15.5 degrees S-15 degrees N) although haptophytes were also a significant component of the population. In contrast, haptophytes dominated the northern oligotrophic region (21 degrees-40 degrees N). Photo-pigment indices indicated that chlorophyll b was mainly associated with prasinophytes and chlorophyll c with diatoms. Elevated photosynthetic carotenoids were due to increased proportions of haptophytes, but also linked with diatoms and dinoflagellates. Photoprotective carotenoids were more prominently associated with Prochlorococcus and to a lesser extent to Synechococcus.

Chemotaxonomic phytoplankton patterns on the eastern boundary of the Atlantic Ocean

Surface pigment data from a transect along the eastern boundary of the Atlantic Ocean was analysed using CHEMTAX to yield more detailed information on the composition of phytoplankton communities. Total chlorophyll a concentrations varied from 0.03 mg m(-3) in a northern oligotrophic region to 30.3 mg m(-3) in the Benguela ecosystem. Diatoms dominated the Benguela, while both diatoms and haptophytes were the major groups in the Canary ecosystem and the temperate NE Atlantic. Prochlorococcus was the most prominent group in the southern oligotrophic region (15.5 degrees S-15 degrees N) although haptophytes were also a significant component of the population. In contrast, haptophytes dominated the northern oligotrophic region (21 degrees-40 degrees N). Photo-pigment indices indicated that chlorophyll b was mainly associated with prasinophytes and chlorophyll c with diatoms. Elevated photosynthetic carotenoids were due to increased proportions of haptophytes, but also linked with diatoms and dinoflagellates. Photoprotective carotenoids were more prominently associated with Prochlorococcus and to a lesser extent to Synechococcus.