This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: As one moves north, Maine's kelp forests are being overtaken by dense mats of carpet-like turf algae. The steady decline of kelp and transition into this new state are altering the ecosystem all the way down to the microbial level, according to a new study in PNAS from Bigelow Laboratory for Ocean Sciences.
The research shows that microbes play an important role in kelp forests—a role that is different on turf-dominated reefs, where the types of microbes present and the chemical compounds they use and produce are fundamentally different. That finding highlights how the loss of foundation species due to environmental change cascades through all levels of the ecosystem, altering basic biochemical processes and species relationships. "We've shown in the past that the loss of kelp leads to changes in the ecology and habitat value of our coastal reefs; we now show that this loss ripples out, all the way down to microbial scales," said senior research scientist Douglas Rasher, the study's senior author.
"The relationships we're unraveling between these underwater forests, their microbial members, and the chemical landscapes they collectively create are invisible to the naked eye but may be critical to kelp forest functioning and resilience in this warming world." Rasher and his team have previously shown how the steady decline of kelp forests driven by human-induced warming affects ecosystem services, biodiversity, nutrient cycling and food web dynamics. It remained unknown, however, what impact this shift had on the resident microbial community and how it functions. This is one of the first studies to grapple with that question in the context of cold-water kelp forests.
The new research also provides a unique perspective by focusing on the microbial community living on the reef rather than in the water column or on individual kelp fronds. "We know from other ecosystems that when these foundational habitats collapse, that has widespread impacts on the microbial community, which is extremely important to the health and functioning of reefs," said the study's lead author, Shane Farrell, a former University of Maine Ph.D. student in Rasher's lab. "We also know that there are distinct microbial communities in the water, on kelp surfaces, and even within the algae; we asked ourselves what would be the broadest and most ecologically important scale to consider, and that's the reef itself." That kind of ecosystem-level approach required a novel synthesis of traditional ecological methods and cutting-edge molecular techniques.
Focusing on six sites—three dominated by turf algae and three by kelp—during both spring and summer, the team combined dive surveys to characterize the algal community; metagenomics to understand what microbial species are present and what biochemical processes their DNA codes for; and metabolomics to get a snapshot of the chemical compounds present at different times. The findings reveal that kelp forests and turf-dominated sites are characterized by taxonomically and functionally different microbial species, all producing and using different suites of chemicals. This aligns with what other scientists have seen in response to similar state shifts on coral reefs and in terrestrial forests.
Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly. The study does not provide measurements of the precise rates of metabolic processes underway on the reef; instead, it provides a snapshot of what microbes and compounds are present, which can be used to infer how the ecosystem is likely functioning. For example, the loss of kelp and the associated loss of canopy cover appear to increase the abundance of photosynthetically active microbial communities.
Extract — continue reading at the source.
