Nearshore Ecosystems
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Intertidal Temperature

INTERTIDAL FLORA AND FAUNA ARE EXPOSED TO WATER AND AIR TEMPERATURES THAT VARY ON DAILY, SEASONAL, AND ANNUAL TIMESCALES. PHOTO CREDIT: MANDY LINDEBERG, NOAA.

Why are we sampling?

Intertidal communities are exposed to both air and water temperatures as tides flow in and out. As such, temperature is a strong driver of intertidal community structure (species composition and abundance; see Intertidal Communities) and can vary from very warm to below freezing in high latitudes. Temperature also can vary significantly on short (daily), seasonal, and longer-term time scales. Currently, we are experiencing more heat wave events but also a general warming due to anthropogenic causes. We monitor intertidal water and air temperatures continuously throughout the year at all sites in each region so that we can evaluate effects of varying temperature on intertidal community structure and trends in abundance of species of interest.

Where are we sampling?

We measure intertidal temperature at the same sites where intertidal communities are monitored in western Prince William Sound (WPWS), Kenai Fjords National Park (KEFJ), Kachemak Bay (KBAY), and Katmai National Park and Preserve (KATM). Data-logging temperature recording devices (HOBOs, see below) are deployed at 2 tidal heights: 0.5m above mean lower low water (MLLW) and 1.5 m above MLLW (low and mid-intertidal zones, respectively).

How are we sampling?

Temperature is measured using HOBO data loggers that record temperature several times per hour every day for the entire year. Because these instruments are deployed in intertidal areas, they record water temperature when the tide is in and air temperature when the tide drops below the level of the data logger. We retrieve and download the instruments every year to continuously track temperature at each site.


THE UNASSUMING PIECE OF GRAY PVC PIPE HOUSES A DATA LOGGER THAT RECORDS AIR AND WATER TEMPERATURES THROUGH THE YEAR. PHOTO CREDIT: DAN MONSON, USGS.

What are we finding?

Nearshore water temperature trends in all four intertidal zones show warming beginning in 2014, corresponding to the large marine heatwave phenomenon (originally termed “the Blob”) detected by more offshore measurements (see Environmental Drivers). Our data confirm that the physical manifestations of this large-scale oceanographic event were expressed in nearshore ecosystems.

INTERTIDAL WATER TEMPERATURE ANOMALIES (DEVIATION FROM THE OVERALL MEAN) AT THE 0.5 M TIDE LEVEL IN THE NORTHERN GULF OF ALASKA: WPWS 2011-2019, KEFJ 2008-2019, KBAY 2013-2019, AND KATM 2006-2019. THE VERTICAL DASHED LINE INDICATES ONSET OF A MARINE HEAT WAVE IN EARLY 2014.