Phytoplankton adapt to changing ocean environments

Abstract

Model projections indicate that climate change may dramatically restructure phytoplankton communities, with cascading consequences for marine food webs. It is currently not known whether evolutionary change is likely to be able to keep pace with the rate of climate change. For simplicity, and in the absence of evidence to the contrary, most model projections assume species have fixed environmental preferences and will not adapt to changing environmental conditions on the century scale. Using 15 y of observations from Station CARIACO (Carbon Retention in a Colored Ocean), we show that most of the dominant species from a marine phytoplankton community were able to adapt their realized niches to track average increases in water temperature and irradiance, but the majority of species exhibited a fixed niche for nitrate. We do not know the extent of this adaptive capacity, so we cannot conclude that phytoplankton will be able to adapt to the changes anticipated over the next century, but community ecosystem models can no longer assume that phytoplankton cannot adapt.phytoplankton | realized niches | climate change | evolution D uring the last several decades, global land temperature has increased by ∼0.3°C per decade (1), and a further increase in global mean air temperatures of 1.1-6.4°C is expected by 2100 (2). The warming of the oceans is resulting in spatially variable changes in sea surface temperature (3, 4), salinity, mixed-layer depth, and the distribution of nutrients. Ocean time series sampled on a monthly basis document intra-and interannual changes in physical forcing and biogeochemistry, providing crucial data for formulating ecosystem models and characterizing how ecosystems respond to climate change (5, 6). We have very high confidence that climate change during the last several decades has influenced the abundance, phenology, and geographic ranges for a wide assortment of species (7-10). Further increases in global temperature may result in significant and nonreversible changes to many populations and communities (11,12). If dispersal rates are rapid relative to the rate of evolutionary adaptation, changes in climate will result in local species being displaced by nonresident species from a regional pool of species that are better adapted to the new conditions (13). When modelers project changes in biotic communities under climate change scenarios, they generally assume that each species has a genetically determined fixed environmental niche and that species' spatial and temporal distributions will be determined by environmental conditions (14-17). A recent model of this type predicts a loss of a third of tropical phytoplankton strains by 2100 with a ∼2°C increase in mean temperature (11); however, paleoecological studies indicate organisms may be much more resilient to climate change than these types of models suggest (18,19).Local populations may be able to acclimate physiologically and then adapt through evolutionary change to gradual climate shifts. We do not know the constraints or timescales req...

Southern Ocean phytoplankton turnover in response to stepwise Antarctic cooling over the past 15 million years

“…The potential for irreversible change in these phytoplankton communities in response to future, geologically abrupt warming in southern high latitudes-a consequence of polar amplification of global warming-remains an open question. This question will be addressed by a growing and diverse body of evidence that spans geological to ecological timescales, such as data on past, regional-, and planetary-scale ecological state changes (37), ecological niche models that are informed by both theory and empirical observations (3,38), observations of adaptive evolution in phytoplankton (39,40), and physiological experiments (41).…”

“…These composites were age-calibrated using paleomagnetic polarity reversal data and one 40 Ar/ 39 Ar age on a volcanic tephra (Table S2). We calculated species-level, lineage-million-year origination and extinction rates (21), which are insensitive to the effects of overall diversity, and from these derived turnover as origination + extinction.…”

Phytoplankton as Key Mediators of the Biological Carbon Pump: Their Responses to a Changing Climate

“…The stoichiometry or elemental composition of phytoplankton is of utmost importance to secondary producers such as copepods, fish and shrimp, because it determines the nutritional quality and influences energy flow through the marine food chains [5]. Climate change may greatly restructure phytoplankton communities leading to cascading consequences for marine food webs, thereby altering the amount of carbon transported to the ocean interior [42]. Figure 3 gives an overview of the various environmental factors that together affect phytoplankton productivity.…”

“…Sustainability 2017, 9, x FOR PEER REVIEW 6 of 17 phytoplankton communities leading to cascading consequences for marine food webs, thereby altering the amount of carbon transported to the ocean interior [42]. Figure 3 gives an overview of the various environmental factors that together affect phytoplankton productivity.…”

Drift in ocean currents impacts intergenerational microbial exposure to temperature

“…The limitation of these studies is that microbial traits are assumed to be constant during model runs, so the microbes themselves are not responding to changes in their environment (18). However, there is increasing evidence that photosynthetic microbes are altering their realized niches in response to contemporary changes in ocean temperature and irradiance (19), and that the geographic origin of microbial ecotypes influences their plasticity (capacity for physiological acclimation) (9,20)-as well as adaptation (21)-at the population level (potentially via increased rate of mitotic mutations) (22), with some ecotypes tolerant of a broad range of temperature and others more thermally specialized (7). Microbes generally experience the ocean as a viscous medium (23), and their motion is therefore predominantly determined by drift with ocean currents (noting that some taxa are motile or regulate their buoyancy) (24).…”