The Blob marine heatwave transforms California kelp forest ecosystems

Abstract

Ocean warming has both direct physiological and indirect ecological consequences for marine organisms. Sessile animals may be particularly vulnerable to anomalous warming given constraints in food acquisition and reproduction imposed by sessility. In temperate reef ecosystems, sessile suspension feeding invertebrates provide food for an array of mobile species and act as a critical trophic link between the plankton and the benthos. Using 14 years of seasonal benthic community data across five coastal reefs, we evaluated how communities of sessile invertebrates in southern California kelp forests responded to the “Blob”, a period of anomalously high temperatures and low phytoplankton production. We show that this event had prolonged consequences for kelp forest ecosystems. Changes to community structure, including species invasions, have persisted six years post-Blob, suggesting that a climate-driven shift in California kelp forests is underway.

Harnessing the Power of Graph Representation in Climate Forecasting: Predicting Global Monthly Mean Sea Surface Temperatures and Anomalies

“…Figure 5 shows the forecasts by GraphSAGE and further adds the selected locations and the major ocean gyres to the map for further analysis. There are several regions in the northeast Pacific, where direct SSTA forecasts by GraphSAGE were outperformed by the persistence, which are areas known for extreme heatwaves, for example, the “Blob” (Michaud et al., 2022). The northeast Pacific is affected by multiple gyres, which feature the North Pacific Current, the Alaska Current, and the California Current.…”

Monitoring Green Sea Turtles in the San Gabriel River of Southern California

“…As such, it is possible that warmer waters from this marine heatwave attracted more green turtles than typical to the SGR during its tenure. In addition, these unusually warm ocean temperatures stunted seasonal upwelling activity, which consequently reduced nutrient availability and caused the collapse of important marine foraging ecosystems, including kelp forests [93,94]. Although not specifically documented along the California coast, the Blob likely damaged Southern California seagrass ecosystems, similar to what has been recorded for seagrass ecosystems affected by marine heatwaves in other parts of the world [95][96][97].…”

Bathymetric origin shapes the physiological responses of Pterygophora californica (Laminariales, Phaeophyceae) to deep marine heatwaves

“…The future of kelp forests in warmer oceans hinges on factors like genetic diversity, phenotypic plasticity, and ecological resilience (Wernberg et al., 2018). These responses, integrated with physiological and morphological variables across biological structures and life stages, play critical roles in determining their reproductive success, vegetative development, and community structure (Andrews et al., 2014; Arafeh‐Dalmau et al., 2019; Liesner et al., 2020; Mabin et al., 2019a; Michaud et al., 2022). Additionally, the combination of MHWs with other stressors, such as low light (Bass et al., 2023; Xiao et al., 2015), nitrate scarcity (Fernández et al., 2020; Mabin et al., 2019b; Umanzor et al., 2021), and hyposalinity (Diehl et al., 2020), may surpass kelps' physiological tolerance thresholds, potentially overwhelming their acclimatory capacity.…”

“…Notably, the recent extreme MHW known as “the Blob” (2013–2016) elevated sea surface temperatures by up to 3.5°C above normal, causing persistent changes in California and Baja California giant kelp forests (Bond et al., 2015; Cavanaugh et al., 2019; Hu et al., 2017). “The Blob” also triggered significant shifts in sub‐canopy and invasive seaweed compositions (Arafeh‐Dalmau et al., 2019; Felix‐Loaiza et al., 2022; Michaud et al., 2022). This event induced strong downwelling anomalies, impacting oceanographic conditions, with potential implications for deep kelp communities (Sen Gupta et al., 2020; Zaba & Rudnick, 2016).…”