Availability of dissolved organic matter offsets metabolic costs of a protracted larval period for Bugula neritina (Bryozoa)

Abstract

For nearly a century researchers have inves tigated the uptake and utilization of dissolved organic matter (DOM) by marine invertebrates, but its contribu tion to their growth, reproduction, and survival remains unclear. Here, the beneWt of DOM uptake was assessed for the marine bryozoan Bugula neritina (Linnaeus 1758) through performance comparisons of individuals in the presence and absence of DOM. The experiments were performed using B. neritina collected from Xoating docks in Beaufort, NC, USA from July to September 2004. Seawater was subjected to ultraviolet irradiation to reduce naturally occurring DOM, and then enriched with either 1 �M of palmitic acid or a mixture containing 1 �M each of glucose, alanine, aspartic acid and glycine. Larvae in DOM-enriched and DOM-reduced treat ments were sampled and induced to metamorphose fol lowing 1, 6, 12, and 24 h of continuous swimming at 25°C. Sampled larvae were assessed for initiation of metamorphosis, completion of metamorphosis, and ancestrular lophophore size to determine the extent to which energy acquired from DOM uptake could oVset the metabolic costs of prolonged larval swimming. DOM treatment had no signiWcant eVect on initiation of metamorphosis, but did have a signiWcant eVect on comple tion of metamorphosis and lophophore size. Larvae swimming in DOM-enriched treatments for 24 h experi enced a 20% increase in metamorphic completion rate, compared to larvae swimming for 24 h in the DOMreduced treatment. In addition, larvae in the amino acid and sugar mixture for 24 h had a signiWcantly larger lophophore surface area and volume (23 and 31%, respectively), compared to larvae in DOM-depleted sea water. To ensure that the increases in performance found in larvae with access to DOM were not due to a decrease in metabolic activity, the respiration rates for these larvae were compared to those of larvae in DOMdepleted seawater. There were no signiWcant diVerences between these treatments, indicating that the increases in performance were due to the energy acquired from DOM. These results clearly show that for B. neritina, DOM uptake results in increased metamorphic success and in the size of the feeding apparatus following an extended larval swimming duration.

Dissolved organic matter influences the timing of embryonic development of the purple sea urchin, Strongylocentrotus purpuratus.

“…As S. purpuratus is sensitive to environmental perturbations early in development this study provides evidence in support of using this methodology for studies of this nature and corroborates the findings of Johnson and Wendt (2007).…”

“…Latent effects are defined as "characteristics that originate in embryonic and larval experiences but become visible only in juvenile or adult stages" (Pechenik 2006). Johnson and Wendt (2007) demonstrated this when they found that lophophores of the ancestrulae of the bryozoan, Bugula neritina, were larger when larvae were swimming in DOM-enriched seawater prior to metamorphosis. The importance of DOM transport to marine invertebrates may manifest in latent effects as embryos and larvae need time to accumulate and store quantities of free amino acids, sugars, and fatty acids before effective utilization can occur.…”

“…For example, Stephens and Schinske (1961) tested for the uptake of glycine by thirty four species from eleven phyla and all species except the six species of Arthropods transported the amino acid. Though the transport of DOM has been shown for many species, very few studies have directly assessed the effects of uptake on ecological parameters such as survival, growth, and reproduction (Johnson and Wendt 2007). Of the eleven phyla and many species for which DOM uptake has been demonstrated, only ten species from four phyla have been directly tested to determine putative realized energetic benefits of transport.…”

“…Lastly, Johnson and Wendt (2007) (Gustafson 1980), trochophore larvae of the red abalone Haliotis rufescens (Jaeckle and…”

An aquatic vertebrate can use amino acids from environmental water

“…Previous studies have documented direct DON uptake by marine invertebrates, thereby shortening the nutrient flow pathway, and improving the growth of individual invertebrates in DON-enriched environmental water [14]. Most studies have used autoclaved or filtered water in their experiments to remove eukaryotic species from the environmental water, but in many cases aquatic bacteria (i.e.…”