Pteropod Project

Using Fatty Acid Profiles to Determine the Relative Condition and Diet of Limacina helicina from the Waters Surrounding Vancouver Island: A Temporal and Spatial Comparison

Overview

During my time at the Dower Lab, University of Victoria, I was involved in a research project focused on Limacina helicina, a species of pteropod, also known as the sea butterfly. These tiny marine snails play a critical role in the marine food web and are considered an indicator species for ocean health, particularly in the context of climate change and ocean acidification.

Research Focus

The project aimed to fill gaps in the scientific understanding of the fatty acid and lipid composition of non-Arctic pteropod species, with a particular focus on L. helicina in the waters surrounding Vancouver Island. We sought to explore the spatial and temporal variations in their fatty acid compositions and use these profiles to infer their relative condition and diet.

Findings

The results of our analyses revealed clear spatial and temporal patterns in the fatty acid profiles of L. helicina, suggesting variations in their diet and condition over time and across different regions surrounding Vancouver Island.

Key Highlights:

• Diet and Feeding Behavior: L. helicina appears to have a mixed diet, primarily feeding on diatoms and dinoflagellates, with little evidence of selective feeding. Their fatty acid composition likely reflects the available prey field, and they do not have a strong connection to the microbial loop nor are they highly carnivorous.

• Temporal Variation: Seasonal changes, particularly the differences between spring and summer, significantly influenced the diet and condition of L. helicina. Pteropods collected in summer 2018 had the highest DHA/EPA ratios, indicating a diet dominated by dinoflagellates, while those collected in spring had lower DHA/EPA ratios, suggesting a diet dominated by diatoms.

• Spatial Patterns: The fatty acid composition of L. helicina did not vary significantly by region or station, suggesting that pteropods in different areas of Vancouver Island's waters may incorporate fatty acid signatures from a variety of prey fields.

• Condition: Pteropods collected during the summer of 2018 were in the poorest condition, as indicated by their low percentage of PUFA, despite having a DHA/EPA ratio within the optimal range for fish diets. This may reflect a poor-quality diet or recent reproductive events.

These findings contribute to our understanding of the ecological role of L. helicina and provide valuable insights into the broader health of marine ecosystems in the area.

Funding

This independent research project was part of a larger project looking at the effects of ocean acidification on pteropods. This research was funded by an NSERC USRA (Natural Sciences and Engineering Research Council of Canada Undergraduate Student Research Award).

This research was supervised by Dr. John Dower and Dr. Cat Stevens, University of Victoria, Victoria, BC, Canada.

A cool NMDS plot I made:

Figure 1. Non-metric multi-dimensional scaling plot to visualize the underlying structure of the fatty acid profiles of L. helicina collected on five cruises: 2018-037, 2018-039, 2019-005, 2019-007, and 2019-044. A Bray-Curtis dissimilarity matrix was used to construct the plot. Vectors refer to individual fatty acids, with the exception of the OBFA vector, which represents the sum of known bacterial fatty acid markers. Ellipses represent two separate clusters of samples determined using hierarchical average-neighbour cluster analysis. The season Spring includes samples collected during March, April, or May; the season Summer includes samples collected in July.