Climate variations may impact the base of the food web along the California coast

March 09, 2020

In a recent study published in Marine Ecology Progress Series, researchers at California Polytechnic State University revealed that in addition to seasonal changes in winds and ocean temperatures, natural climate cycles greatly influenced the base of the food web at the Cal Poly Pier in San Luis Obispo Bay, an embayment located in Central California in the California Current Large Marine Ecosystem. Like seasons that drive recurring changes in ocean and atmospheric patterns every year, natural climate cycles drive rhythmic changes in these patterns over longer cycles.

The most commonly known natural climate cycle is the El Niño-Southern Oscillation (ENSO), which alters ocean and atmospheric weather patterns over the equatorial Pacific every three to eight years, with cascading effects on global weather patterns. However, along the California coast, other climate cycles such as the Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) can influence local ecosystems on cycles of a few years to a few decades. The study found that while local changes in temperature and nutrients influenced the overall community of phytoplankton that was present in San Luis Obispo Bay throughout the year, the state of these long-term climate cycles, i.e., the up or down points in these oscillating climate patterns, influenced the timing of when different phytoplankton groups appeared or if they appeared at all.

Primary producers such as phytoplankton form the base of the marine food web. These phytoplankton are eaten by small consumers like zooplankton and larval fish. As a result, changes at the base of the food web can affect organisms across multiple trophic levels in marine ecosystems. Researchers at Cal Poly have been collecting seawater samples over the last decade to gain insight into short term (seasonal) and long-term (interannual) changes in the base of the food web

"We care about the different types of phytoplankton because they have different impacts on the ecosystem," said Cal Poly biology professor Alexis Pasulka. "Some types provide better quality food for organisms like larval fish, whereas some types can produce toxins and have negative effects on local ecosystems."

Harmful algal blooms (HABs) are proliferations of aquatic algae that disrupt ecosystems and impair water quality. The environmental impacts of HABs can be sudden, severe and lethal across all levels of aquatic and terrestrial food webs. The types of phytoplankton that more commonly form HABs, dinoflagellates, are often associated with warmer waters that are less mixed by local winds.

"The phytoplankton are responding to changes in environmental conditions driven by the physics and motions of the ocean," said Cal Poly physics professor Ryan Walter. "These changes are not only happening seasonally but also over much longer time scales due to natural climate cycles like ENSO and PDO, as well as climate change due to human activity."

This study highlights that during the warm state of the PDO, i.e., the up in the PDO climate cycle, dinoflagellate blooms appeared more consistently in the fall and sometimes earlier in the seasonal cycle than during the cold state. This warm state of the PDO was characterized by increased surface temperatures and increased stratification (temperature changes with depth), both of which are expected to increase in the future due to global warming. This study may provide a glimpse into the future and a clue as to how the base of the food web and the prevalence of harmful algal blooms might respond to climate change-driven ocean warming.
-end-
This work was led by Cal Poly biology undergraduate Alex Barth - who is now pursuing his Ph.D. at the University of South Carolina - under the guidance of Pasulka and Walter, as well as senior research scientist Ian Robbins. This work was funded by the Southern California Coastal Ocean Observing System as part of the California Harmful Algal Bloom Monitoring and Alert Program.

California Polytechnic State University

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.