Traits Shared by Marine Megafauna and Their Relationships With Ecosystem Functions and Services

Abstract

Traditional ecological research has focused on taxonomic units to better understand the role of organisms in marine ecosystems. This approach has significantly contributed to our understanding of how species interact with each other and with the physical environment and has led to relevant site-specific conservation strategies. However, this taxonomic-based approach can limit a mechanistic understanding of how environmental change affects marine megafauna, here defined as large fishes (e.g., shark, tuna, and billfishes), sea turtles, marine mammals, and seabirds. Alternatively, an approach based on traits, i.e., measurable behavioral, physiological, or morphological characteristics of organisms, can shed new light on the processes influencing structure and functions of biological communities. Here we review 33 traits that are measurable and comparable among marine megafauna. The variability of these traits within the organisms considered controls functions mainly related to nutrient storage and transport, trophic-dynamic regulations of populations, and community shaping. To estimate the contributions of marine megafauna to ecosystem functions and services, traits can be quantified categorically or over a continuous scale, but the latter is preferred to make comparisons across groups. We argue that the most relevant traits to comparatively study marine megafauna groups are body size, body mass, dietary preference, feeding strategy, metabolic rate, and dispersal capacity. These traits can be used in combination with information on population abundances to predict how changes in the environment can affect community structure, ecosystem functioning, and ecosystem services.

Functional diversity of marine megafauna in the Anthropocene

“…Functional trait analyses have long been used to gauge the consequences of species loss for ecosystem functioning, because traits better define how organisms interact with their environment and each other than do simple taxonomic measures (48). This trait-based approach may be especially relevant for marine megafauna, which, because of their size and mobility, are difficult to study using traditional experimental approaches (1,49). Current global marine megafaunal functional diversity is highly influenced by traits associated with cross-realm movements.…”

Biological traits of seabirds predict extinction risk and vulnerability to anthropogenic threats

“…Specifically, globally threatened species share a distinct subset of similar traits that are associated with a higher risk of extinction. Therefore, the loss of threatened species, such as wide-ranging albatross and shearwaters, may have direct implications for ecosystem functioning such as trophic regulation, nutrient transportation and community shaping (Graham et al, 2018;Tavares et al, 2019). We further find non-threatened species have relatively unique ecological strategies and limited redundancy.…”

“…Furthermore, selecting meaningful and interpretable species' traits can relate to species' vulnerability to threats and their contribution to ecosystem functions (Table 1). For example, a species' diet captures regulation of trophic-dynamics and nutrient storage functions, and its sensitivity to changes at lower trophic levels (Tavares, Moura, Acevedo-Trejos, & Merico, 2019). Combinations of traits can summarise a species' ecological role (Brum et al, 2017), and species can be grouped based on ecologically similar strategies .…”

Mortality of seabirds migrating across the tropical Atlantic in relation to oceanographic processes

“…A total of 34% of the 1757 birds in our data were recovered alive, a further indication of the role of wave height as a proxy for storm intensity. Inter and intraspecific trait variability related to bird survival abilities, such as preferred diet, feeding strategy, body mass and age (Tavares et al , ), can help us understand how these organisms respond to oceanographic conditions. Predictive models should consider that, on average, about 17% of dead birds are recovered on beaches (Munilla et al , ), thus bird deaths estimated by beach monitoring programmes represent only a small component of bird mortality.…”