Throughout May, we will be featuring all the articles that were shortlisted for the Harper Prize 2020. The Harper Prize is an annual award for the best early career research paper published in Journal of Ecology.
Alizée’s article, Seaweed functional diversity revisited: Confronting traditional groups with quantitative traits was one of the eight papers shortlisted for this year’s award.
I always had a strong interest in the marine realm, having had the chance to snorkel and dive my way around the seven seas from an early age, as well as in plants — or any plant-like organism for that matter. Therefore, when I was given the opportunity to study what I wanted during my undergraduate degree, it seemed natural to direct my research towards the intersection of these two fields; seaweeds. I first wrote a literature review of kelp morphological and physiological adaptations to their environment as an assignment in my second year of university. Luckily, it caught the attention of one of its reviewers, who proposed that we developed a project as part of my third year research on the functional ecology of macroalgae.
There began my journey into the at-first confusing but eventually gratifying world of functional ecology as part of the Griffin lab at Swansea University, UK. I graduated from my BSc with First Class Honours in Marine Biology in 2014. I was then awarded a merit scholarship from Swansea University to pursue an MRes in Biosciences, which I completed in 2015. I obtained a scholarship from the same university and embarked on a PhD to further my research, with the aim of developing a comprehensive database of macroalgal functional traits, or “traitabase”, to mechanistically assess the linkages between macroalgae and ecosystem functioning. The paper shortlisted here for the Harper Prize is the first publication to come out of my PhD as well as my first publication overall, and is the result of a combined seven years of trait screening and analysis. This paper is all the more important to me as it represents my overcoming of many hardships, including debilitating symptoms and medical limbo from a suspected hypermobility disorder (HSD/hEDS).
Seaweed, or macroalgae, are thought by many as more of a slimy, sticky inconvenience of the beach than an ecological cornerstone. Yet, macroalgae serve as the main primary producers of coastal ecosystems in the North East Atlantic, and provide essential ecosystem functions and services such as carbon sequestration, habitat and food provisioning for commercially-important fish, and a growing source of food or high-value products for a variety of industries. Assessing the relative contribution of macroalgal species to ecosystem functions and services has long been facilitated by the use of form-based functional groups, which remains the most common functional approach in the field. However, the ability of such functional groups to capture macroalgal functional traits and ecological roles has seldom been assessed.
In our paper, “Seaweed functional diversity revisited: Confronting traditional groups with quantitative traits”, my fellow PhD student Laura Cappelatti, my supervisor John Griffin and I addressed this fundamental question by quantifying the ability of four form-based, “traditional” grouping approaches — two schemes based on gross morphology and anatomy as well as two categorisations of vertical space use — in capturing the functional trait space of an unprecedented dataset of macroalgal traits spanning 95 species and 12 traits (Figure 1). We found that morphology and anatomy-based groups explained about a third of macroalgal functional variation and that classifications of vertical space use accounted for roughly a quarter. While those figures are far from insignificant, we found that traditional functional groups largely overlapped (suggesting low precision) with extensive mismatch with underlying trait expression (suggesting low accuracy) (Figure 2). We also found that traditional functional groups differed in their ability to accurately and precisely capture underlying functional expression. In fact, traditional groups were massively reworked when classifying macroalgae into trait-based, post hoc “emergent groups”; for example, the “thick leathery” group—consisting mostly of kelps and fucoids— was split into two emergent groups and most of the species of the “coarsely branched”/“corticated” group were reallocated to several emergent groups, while filamentous and articulated calcareous species tended to be grouped together regardless of the grouping scheme.
We found that a parsimonious nine-group emergent classification explained 69 % of macroalgal functional expression and offer this as a potentially ecologically powerful alternative to form-based grouping approaches. Still, we ultimately advocate for coordinated trait screening efforts and the use of direct functional traits in the aim of establishing stronger, more general quantifications of macroalgal ecological roles.
Throughout my studies, my research has been motivated by the realisation that the field of algal functional ecology stood largely separate from that of other primary producers and that it remained largely dominated by the use of functional groups established in the early 1980s with limited testing of their ecological relevance. While seminal works such as those of Mark and Diane Littler in the 1980s and Steneck and Dethier (1994) motivated the development of holistic, mechanistic linkages between form and function, macroalgal functional ecology has been largely limited to rather small-scale, isolated studies of response to environmental conditions and effect on ecosystem functions — mainly, primary productivity. This is a stark contrast to the field of plant functional ecology, where researchers have aimed to establish general unifying patterns of primary producer ecological variation, to the point that large functional trait databases have been built and have revealed defined axes of global plant adaptive strategies (Díaz et al., 2016). The field is now moving towards the inclusion of most primary producers including non-vascular plants such as mosses and ferns, but also aquatic plants such as seagrasses, saltmarsh grasses, and mangrove trees.
Therefore, the overarching aim of my research is to push the field of macroalgal functional ecology further towards general patterns of functional variation and ecological strategies, linking in the process response and effect in order to more fully comprehend macroalgal ecological roles. While macroalgae present fundamental physiological differences to (in particular, vascular) plants, they could eventually be placed along existing spectra of primary producer variation.
I find myself frequently stunned by how beautiful and diverse seaweeds are, both in their natural habitat and in the lab under a microscope or laid out on a lightbox. Scanning and photographing samples was carried out to measure functional traits such as surface area, perimeter and branching order, and it occurred to me that this process was not too far off the 19th century tradition of seaweed pressings and cyanotypes, made famous by British botanist Anna Atkins. Therefore, I assembled a mosaic of some of the “pressings” done and coloured it in the style of a cyanotype. My image won the Beauty in Nature award as part of Swansea University’s Research as Art 2019 competition. Similarly, a mosaic of seaweed pressings I created was shortlisted for the Hilda Canter-Lund prize of the British Phycological Society in 2017.
We announced the winners for the Harper Prize 2020 at the end of April, find out more on the blog.
You can also read all 8 shortlisted papers in our new Harper Prize 2020 Virtual Issue. These articles are free to read for a limited time!