Nearshore

Studies conducted using a network of moored sensors in Homer, Seldovia, Kasitsna Bay, Jakalof Bay and Bear Cove found that the Kachemak Bay region has some of the largest pH fluctuations in the world in terms of hourly changes. It is apparent that nearshore organisms in Kachemak Bay are being exposed to unstable, non-static pH conditions on tidal and daily cycles. Researchers believe it’s possible that the large natural variation in seawater acidity throughout the day would have historically required organisms to adapt to withstand these dramatic shifts in local carbon chemistry conditions. This means that organisms that are adapted to these local habitats may be more resilient to future low pH conditions (acidification), and places of extreme pH fluctuation could potentially serve as refuges for certain species.

It is important to note that Kachemak Bay is home to a number of successful oyster farms whose production may be impacted by future ocean acidification. As sensors continue to collect data, researchers will be able to expand on this time-series to better determine and quantify anthropogenic (human-caused) CO₂ intrusion in Kachemak Bay in the coming years.

Kodiak Archipelago monitoring includes a Burke-o-Lator at the Kodiak NOAA Laboratory and a community sampling program run by the Kodiak Area Native Association (KANA). Samplers in four communities collect water samples which are processed at the Kodiak Burke-o-Lator for analysis of ocean acidification parameters.

The data collected as part of this program are considered baseline data because they allow researchers to measure environmental conditions that have never been monitored to this extent on Kodiak Island. Tribal communities can then use these data to better understand, adjust, and adapt to changing water quality conditions that can impact subsistence resources, economic development, and overall livelihoods. Researchers at the Kodiak Laboratory also use these data in their multi-year experiments designed to assess the physiological response of early life history stages of commercial crab species, while estimating the potential for acclimation and adaptation to the marine chemistry changes expected with ocean acidification.

In 2017, a vessel of the Alaska Marine Highway named Columbia was instrumented with sensors to gather information on ocean acidification along the Inside Passage between Bellingham, WA and Skagway, AK. The goal of this effort was to gain a better understanding of the environmental and human-caused drivers of ocean acidification along the coast, to investigate seasonal variability in ocean acidification across the region and ecosystem change to date, and to explore the ecosystem’s potential resilience to a future atmospheric CO₂ that corresponds with a 1.5 C warmer world. The data collected from the ferry has shown that seasonal patterns are changing. This information provides an important baseline to assess the changes in ocean acidification and corrosivity (pH and Ωarag) that have occurred as a result of the growing contribution of human-caused CO₂ in these waters.

Here are a few of the takeaways from the Columbia study. For more information about current and future nearshore conditions, visit the Southeast Alaska Regional Conditions page.

• The Alexander Archipelago exhibited large variability in acidity and corrosivity relative to other areas along the Inside Passage. This was especially true for northern Southeast Alaska (Chatham Strait, Frederick Sound, Stevens Passage, Peril Strait, and Lynn Canal).
• Contrasting with these highly variable areas, Sergius Narrows and Wrangell Pass had low variability owing to the influence of persistent tidal mixing.
• In terms of severity, Lynn Canal and Wrangell Narrows were quite corrosive (severe Ωarag values) but less acidic (less severe pH).
• Areas exposed to the open continental shelf, such as Dixon Entrance and near Sitka, generally had less severe and variable acidity and corrosivity (pH and Ωarag) compared to confined waters along the Inside Passage.

A recent study looking at ocean acidification along the Arctic coast of Alaska has provided scientists with a new perspective on the relationship between local environmental drivers of ocean acidification and the role of lagoons in CO₂ exchange. Researchers deployed a device called a SeaFET in the Kaktovik Lagoon. This lagoon is a body of water adjacent to the community of Kaktovik, the traditional homeland of the Qaaktuġvigmiut, about 100 miles east of Prudhoe Bay. The sensor collected a number of high frequency measurements including pH (acidity) for nearly a full calendar year, capturing both ice-covered and ice-free phases.

Several illuminating trends have emerged in the data.

• Kaktovik Lagoon appears to exhibit some of the most dramatic fluctuations in pH (acidity) ever recorded. Gaining a better understanding of these dynamic conditions will lend insight into the community structure of the resident species in the lagoon, which includes a rich diversity of anadromous fish. Researchers are interested in studying the mechanisms of adaptation that local species have used to survive these dramatic hourly fluctuations.
• The relationship between seawater pH (acidity) and salinity (salt content) ranges across a spectrum that changes by season. When the seawater is ice-free, the relationship between these two variables is either positive or neutral, while the ice-covered season resulted in a negative correlation. This isn’t what researchers were expecting to find. This deviation from the norm suggests that the physical and biological processes that influence seawater acidity (pH) are dynamic and susceptible to future change – particularly from freshwater runoff and shifts in the way organisms who live there feed and produce CO₂.
• Bodies of water or other biomes on earth can act either as CO₂ “sinks” by absorbing CO₂ from the atmosphere, or as “sources” by emitting CO₂ into the atmosphere. The world’s oceans have generally acted as carbon sinks, where the absorption of additional carbon causes an increase in acidity and results in the process we know as ocean acidification. However, depending on local or regional chemical and biological processes, bodies of water can also be sources of CO₂ through outgassing – particularly nearshore estuaries . The Western Arctic has long been considered a large sink for atmospheric CO₂ that is susceptible to rapid acidification relative to other oceanic regions. However, the findings from this project suggest that the lagoon ecosystems may not follow this general pattern. More lagoon-specific research is necessary to gain a better understanding of this possible role reversal. Since about 50% of the Alaskan Arctic is made up of coastal lagoons, it is possible that new findings could change the estimates researchers are making about the magnitude of the Arctic’s CO₂ sink.

The study underscores the need to expand high frequency measurements of ocean acidification variables in Arctic lagoons to provide insights into local drivers, species adaptations and the role of these water bodies in removing or adding CO₂ to the atmosphere.

Seasonal Phases of an Arctic Lagoon: Miller et al 2021

• An autonomous pH sensor was deployed in Kaktovik Lagoon from 2018 – 2019 to capture two summer phases of open water (non-ice covered) and one closed phase (ice covered).

Results

• Patterns of pH variability from year-to-year during the open phase are not relatable.
• 2018, overall pH appeared to be higher and less sensitive to changes in salinity, whereas in 2019 salinity changes correlated with changes in pH.
• 2019 recorded an overall lower pH, CO₂ emissions from the lagoon were positive whereas CO₂ emissions in 2018 were minimally positive.
• This demonstrates that biological processes in the lagoon sediment and overlying water can be quite variable from year-to-year and dramatically affect whether or not the lagoon absorbs or emits CO₂ to the atmosphere.

Abiotic Drivers of Arctic Nearshore Fish Abundance: Khalsa et al 2021

• High-frequency in situ measurements of pH, temperature, salinity, and dissolved oxygen were paired with daily fish catches in nearshore Beaufort Sea
• Generalized additive models (GAMs) were used to describe responses to nearshore environment for 18 fish species

Results

• Relationships between abundance and the physicochemical environment were variable between species and reflected life history.
• Each abiotic covariate was significant in at least one GAM, exhibiting both nonlinear and linear associations with abundance.
• Temperature was the most important predictor of abundance and was significant in GAMs for 11 species.
• pH was a significant predictor of abundance for 6 species: Arctic cod, broad whitefish, Dolly Varden, ninespine stickleback, saffron cod, and whitespotted greenling.
• Broad whitefish and whitespotted greenling abundance was positively associated with pH while Arctic cod and saffron cod abundance was negatively associated with pH.

Marine CO2 system variability determined from an Alaskan Ferry: Evans et al 2021

• From 2017, the Alaska Marine Highway System M/V Columbia has served as a platform for surface underway data collection while conducting twice weekly ~1600-km transits between Bellingham, Washington and Skagway, Alaska.
• This 2-year dataset allowed for the assessment of marine CO2 system patterns along the Inside Passage. Surface water pH and aragonite saturation state (Ωarag) were determined using the pCO2 data with alkalinity from a regional salinity-based relationship, which was evaluated with discrete seawater samples and underway pH measurements.

Results

• Low pH and corrosive (Ωarag < 1) Ωarag conditions were seen during winter and in persistent tidal mixing zones;
• Corrosive Ωarag values were also seen in areas that receive significant glacial melt in summer;
• ‘Time-of-detection’ (how long it takes to calculate the rate of ocean acidification) was computed and revealed that tidal mixing zones may be sentinel observing sites with relatively short time spans of observation needed to capture the trend in seawater pCO₂ equivalent to the contemporary 25 atmospheric CO₂ increase.
• Anthropogenic CO₂ was estimated and showed notable time and space variability. We theoretically considered the change in hydrogen ion concentration ([H+]), pH, and Ωarag over the industrial era and to an atmospheric pCO₂ level consistent with a 1.5°C warmer climate and revealed greater changes in [H+] and pH in winter as opposed to larger Ωarag change in summer.
• In addition, the contemporary acidification signal everywhere along the Inside Passage exceeded the global average, with Johnstone Strait and the Salish Sea standing out as potential bellwethers for 30 biological OA impacts.
• In theory, roughly half the acidification signal experienced thus far over the industrial era may be expected over the coming 15 years with an atmospheric CO₂ trajectory that continues to be shaped by fossil-fuel development.