Revisiting the 'bank of microscopic forms' in macroalgal-dominated ecosystems.

Abstract

Theoretical ecological models, such as succession and facilitation, were defined in terrestrial habitats, and subsequently applied to marine and freshwater habitats in intertidal and then subtidal realms. One such model is the soil seed bank, defined as all viable seeds (or fruits) found near the soil surface that facilitate community restoration/recovery. "Banks of microscopic forms" have been hypothesized in aquatic habitats and recent work from aquaculture has highlighted dormancy in algal life cycle stages. To reinvigorate the discussions about these algal banks, we discuss differences in life cycles, dispersal, and summarize research on banks of macroalgal stages in aquatic ecosystems that may be easier to explore with modern advances in molecular technology. With focus on seminal work in global kelp forest ecosystems, we present a pilot study in northern California as proof of concept that Nereocystis luetkeana and Alaria marginata stages can be detected within kelp forests in the biofilm of rocks and bedrock using targeted primers long after zoospore release. Considering the increased interest in algae as an economic resource, [blue] carbon sink, and as ecosystem engineers, the potential for "banking" macroalgal forms could be a mechanism of resilience and recovery in aquatic populations that have complex life cycles and environmental cues for reproduction. Molecular barcoding is becoming an important tool for identifying banks of macroalgal forms in marine communities. Understanding banks of macroalgal stages, especially in deforested habitats with intense disturbance and grazer pressure, will allow researchers and marine resource managers to facilitate this natural process in recovery of the aquatic system.