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

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.

Field Collection and Laboratory Maintenance of Canopy-Forming Giant Kelp to Facilitate Restoration.

Canopy-forming kelps are essential foundation species, supporting biodiversity and providing ecosystem services valued at more than USD$500 billion annually. The global decline of giant kelp forests due to climate-driven ecological stressors underscores the need for innovative restoration strategies. An emerging restoration technique known as 'green gravel' aims to seed young kelps over large areas without extensive underwater labor and represents a promising restoration tool due to cost-effectiveness and scalability. This video article illustrates a protocol and tools for culturing giant kelp, Macrocystis pyrifera. It also provides a resource for further studies to address the successes and limitations of this method in field settings. We outline field and laboratory-based methods for collecting reproductive tissue, sporulating, inoculating, rearing, maintaining, and monitoring substrates seeded with early life stages using the 'green gravel' technique. The protocol simplifies and centralizes current restoration practices in this field to support researchers, managers, and stakeholders in meeting kelp conservation objectives.

Global kelp forest restoration: past lessons, present status, and future directions.

Kelp forest ecosystems and their associated ecosystem services are declining around the world. In response, marine managers are working to restore and counteract these declines. Kelp restoration first started in the 1700s in Japan and since then has spread across the globe. Restoration efforts, however, have been largely disconnected, with varying methodologies trialled by different actors in different countries. Moreover, a small subset of these efforts are 'afforestation', which focuses on creating new kelp habitat, as opposed to restoring kelp where it previously existed. To distil lessons learned over the last 300 years of kelp restoration, we review the history of kelp restoration (including afforestation) around the world and synthesise the results of 259 documented restoration attempts spanning from 1957 to 2020, across 16 countries, five languages, and multiple user groups. Our results show that kelp restoration projects have increased in frequency, have employed 10 different methodologies and targeted 17 different kelp genera. Of these projects, the majority have been led by academics (62%), have been conducted at sizes of less than 1 ha (80%) and took place over time spans of less than 2 years. We show that projects are most successful when they are located near existing kelp forests. Further, disturbance events such as sea-urchin grazing are identified as regular causes of project failure. Costs for restoration are historically high, averaging hundreds of thousands of dollars per hectare, therefore we explore avenues to reduce these costs and suggest financial and legal pathways for scaling up future restoration efforts. One key suggestion is the creation of a living database which serves as a platform for recording restoration projects, showcasing and/or re-analysing existing data, and providing updated information. Our work establishes the groundwork to provide adaptive and relevant recommendations on best practices for kelp restoration projects today and into the future.

Marine deforestation leads to widespread loss of ecosystem function.

Trophic interactions can result in changes to the abundance and distribution of habitat-forming species that dramatically reduce ecosystem functioning. In the coastal zone of the Aleutian Archipelago, overgrazing by herbivorous sea urchins that began in the 1990s resulted in widespread deforestation of the region's kelp forests, which led to lower macroalgal abundances and higher benthic irradiances. We examined how this deforestation impacted ecosystem function by comparing patterns of net ecosystem production (NEP), gross primary production (GPP), ecosystem respiration (Re), and the range between GPP and Re in remnant kelp forests, urchin barrens, and habitats that were in transition between the two habitat types at nine islands that spanned more than 1000 kilometers of the archipelago. Our results show that deforestation, on average, resulted in a 24% reduction in GPP, a 26% reduction in Re, and a 24% reduction in the range between GPP and Re. Further, the transition habitats were intermediate to the kelp forests and urchin barrens for these metrics. These opposing metabolic processes remained in balance; however, which resulted in little-to-no changes to NEP. These effects of deforestation on ecosystem productivity, however, were highly variable between years and among the study islands. In light of the worldwide declines in kelp forests observed in recent decades, our findings suggest that marine deforestation profoundly affects how coastal ecosystems function.