Kelp beats the heat

December 13, 2016

In early 2014, when a large-scale marine heat wave in the Pacific Ocean produced temperature anomalies greater than anything seen since recordkeeping began in the early 1900s, marine scientists saw something else, too: opportunity.

Ocean researchers at UC Santa Barbara quickly seized the chance to evaluate the sentinel status of giant kelp forests along the Southern California coastline as an indicator of climate change. They expected forests of giant kelp (Macrocystis pyrifera), known to be sensitive to such increases as well as to the resulting low-nutrient conditions, to respond quite rapidly to a rise in water temperature.

However, to the scientists' surprise, that was not the case. The kelp, they discovered, was all right. Their findings appear in the journal Nature Communications.

"The response that we saw in kelp was really no different than what we'd seen in our temporal record," explained lead author Daniel Reed, deputy director of UCSB's Marine Science Institute (MSI). "The values were low but not necessarily lower than what we'd seen during cool-water years."

Giant kelp does not have the capacity to store nutrients for very long (only about three weeks), and in the absence of new nutrients, the kelp cannot support its rapid growth of about 2 percent per day. The standing biomass -- the amount of living kelp present at a given time -- is relatively transitory and turns over about seven times a year.

"Each frond only lives about three to four months," Reed said. "So when you have something that grows rapidly and doesn't live long, you would expect its standing biomass to respond rapidly if it's subjected to really adverse growing conditions for a long time."

The researchers used kelp records from a 34-year time series of data taken by Landsat satellites, which -- among many other characteristics -- measured kelp canopies. The investigators analyzed kelp biomass from Santa Barbara to San Diego through time and related it to sea surface temperatures at those sites.

The data showed some large positive temperature anomalies that were unprecedented. For example, in September 2015, the water in the Santa Barbara Channel averaged 4.5 degrees Celsius higher than normal for the entire month. Daily anomalies went as high as 5.5 degrees Celsius. Despite these high temperatures, the team saw no dramatic response by giant kelp whose biomass remained within the range observed during the decades-long time series when the water was cooler.

"Nobody knows how this warming event relates to climate change, other than we've not seen this before," said co-author Libe Washburn, an oceanographer at the MSI and a professor in UCSB's Department of Geography. "That's somewhat alarming, but this work may provide some insight into how these kelp forests would respond to future climate warming."

The team also examined changes in understory algae, invertebrates and fishes of the giant kelp ecosystem and found that they didn't show much of a response to the warming event either. Sea urchins and sea stars were the exception as they declined dramatically due to a disease that was linked to the warm-water event.

"The fact that we did not see drastic responses in the rest of the community tells us that we don't know everything we think we know about this system and about its ecology," Reed noted. "The results have caused us to pursue lines of research that try to understand how this happens. More importantly, the findings underscore the value of long-term data in terms of trying to tease apart these trends."
-end-
Other UCSB co-authors include Tom Bell, Robert Miller and Shannon Harrer. Andrew Rassweiler of Florida State University also was a contributor.

This research was supported by the National Science Foundation's Long Term Ecological Research program, the NASA Biodiversity and Ecological Forecasting program, the Bureau of Ocean and Energy Management Environmental Studies program and the National Oceanic and Atmospheric Administration in support of the Santa Barbara Channel Marine Biodiversity Observation Network.

University of California - Santa Barbara

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.