A new paper in the Journal of Estuarine, Coastal and Shelf Science revealed that the Puyuhuapi fjord in the Aysen region of Chile houses over 1,600 species of benthic fauna, which are basically underwater biology. The paper was published by Federico Betti and his team from the marine zoology lab of DISTAV Genoa University in Italy. The Chilean fjords are one of the most productive areas in the world and a crucial hotspot of biodiversity in cold-temperate climates. Benthic faunas such as algae and microbes represent interesting species that play important ecological roles and could serve as indicators of human disturbance on pristine ecosystems.
In fact, the intriguing aspects of the research extends to the research methodology. The team explored the fjords via scuba diving to photograph the species underwater. Even in summer, water temperatures in the fjord are only about 10 degrees Celsius. In this challenging cold-water environment, they had to get in wetsuits to photograph aquatic species at depths of up to 30m. Thereafter, the taxa were identified and categorized into 12 main bottom-dwelling species groups including corals/corallinales, cyanobacteria, algae, cnidaria (i.e. jellyfish, sea anemones) and molluscs. The area they occupied was also measured, noting temperature and conductivity (a variable which affects dissolved ions) of the water.
“The main goals were to describe the benthic communities of Puyuhuapi Fjord and how the benthic communities change in different environmental conditions,” lead researcher Betti told Glacierhub. The study was a collaboration with the Centre for Investigation of the Ecosystems in Patagonia (CIEP), which makes policy recommendations and has been conducting research in the Puyuhuapi fjord for a few years. Puyuhuapi Fjord represents a rather closed fjord, causing the communities to be highly affected by freshwater inputs, according to Betti et al. Meltwater from the coastal glaciers by the fjord is its main source of freshwater.
Molluscs, cnidarians (organisms containing trigger cells that can shoot toxins into others) and sponges are the groups of benthic fauna with highest biodiversity. The team noted that stations located along the lower portions of the fjord differed noticeably from the upper, more inland areas in terms of total percentage cover but not for taxonomic group diversity. A decrease in benthic-life abundance is found at the top of the fjord, as the mouth of the river brings nutrients and sediments, causing silting. There is also a vertical gradient, with highest diversity found at intermediate depths. On average, benthic life abundance also decreased from the shallow to deep regions. In horizontal, as well as vertical terms, overall abundance of organisms and diversity of organisms are distributed differently. While the former is a result of organic material input, the latter is due to the high turbidity of the water causing limited light penetration with depth. Algae represents the most significantly affected community due to its high dependence on light penetration for photosynthesis.
Salinity of water also directly influences the types of species observed. Saline water exists at 7m depth onwards, which is most prominent at the upper sections, where the mouth of the river at the top of the fjord supplies low density fresh estuarine water which spreads across the entire fjord. The two strata house different assemblages with gastropods comprising snail, slugs and limpets dominating the superficial layer and echinoderms such as starfish and sea urchins in the shallow saline region.
The main ecological threat comes from salmon farming, with many salmon-farming cages proliferating the Puyuhuapi region. “Escaped salmons are colonizing the fjords, and it can be a problem for the ecosystem. Antibiotics can enter the food webs, when the benthic communities living close or below the cages are strongly impacted by fecal pellets, food pellets, anoxia and sedimentation,” Betti explains. “In fact, we have collected some sponges that I believe the CIEP is analyzing for antibiotics coming from the cages,” he added.
Substantial growth of fish and mussel farming has occurred in the last decade, leading to sedimentation and nutrient pollution. Being a closed fjord, the area is experiencing less ocean circulation, thus the problem of increased nutrients and antibiotics is accentuated. Only the lower portion of the fjord has turbulent waters, mainly due to a circular ocean current that drives salty and dense water into the system. However, the salty water is immediately forced under less dense fresh water, causing it to lose power and barely reaching the innermost portion of the fjord. Due to limited penetration of ocean water, biodiversity decreased inland as nutrient levels in calm waters increases, the study found.
The team is currently still conducting research on the Puyuhuapi fjord region to explore the relationship between biodiversity and water conditions at intermediate depths. This requires quantifying the variety of species, as well as concentration of oxygen and metal ions in the water, among other parameters unique to different species. Ultimately, they hope to designate the fjord as a Marine Protected Area by justifying its rich biodiversity and sensitivity to anthropic disturbances.