Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), produced by cyclic GMP-AMP synthase (cGAS), stimulates the production of type I interferons (IFN). Here we show that cGAMP activates DNA damage response (DDR) signaling independently of its canonical IFN pathways. Loss of cGAS dampens DDR signaling induced by genotoxic insults. Mechanistically, cGAS activates DDR in a STING-TBK1-dependent manner, wherein TBK1 stimulates the autophosphorylation of the DDR kinase ATM, with the consequent activation of the CHK2-p53-p21 signal transduction pathway and the induction of G1 cell cycle arrest. Despite its stimulatory activity on ATM, cGAMP suppresses homology-directed repair (HDR) through the inhibition of polyADP-ribosylation (PARylation), in which cGAMP reduces cellular levels of NAD+; meanwhile, restoring NAD+ levels abrogates cGAMP-mediated suppression of PARylation and HDR. Finally, we show that cGAMP also activates DDR signaling in invertebrate species lacking IFN (Crassostrea virginica and Nematostella vectensis), suggesting that the genome surveillance mechanism of cGAS predates metazoan interferon-based immunity.

Oyster reef restoration is pursued at numerous places worldwide, yet little is known about how ecosystem function changes as these reefs develop. In this study, we used the noninvasive aquatic eddy covariance technique to measure the in situ oxygen flux of 4 intertidal sites on the Virginia (USA) coast: a natural oyster reef, 2 restoration reefs, and a mudflat. Oyster densities of the 3 reefs were 350, 295, and 186 oysters m −2. Mean summer values of nighttime oxygen flux (Flux DARK) were −488, −428, −300, and −56 mmol m −2 d −1 over the natural reef, 2 restoration reefs, and mudflat, respectively. All 4 sites had smaller daytime vs. nighttime oxygen uptake, with mean summer differences between Flux DARK and Flux LIGHT of 360, 250, 239, and 27 mmol m −2 d −1. Light was an important short-term driver of daytime reef oxygen flux due to its effect on microalgal photosynthesis. All 3 oyster reefs were significantly heterotrophic, with summer net ecosystem metabolism values ranging from −157 to −298 mmol m −2 d −1. Flux DARK values were similar across the 3 reefs when normalized by density, with values between −1.8 and −2.3 mmol m −2 d −1 oyster −1. This study represents the most detailed measurements to date of in situ oyster reef oxygen flux, and shows that benthic microalgae can significantly impact reef oxygen dynamics. Flux DARK values scale with oyster density, and consequently can be used as a metric for reef restoration success.

Invasive macroalgae represent a growing global concern, yet there has been little research detailing their effects on native ecosystem metabolism and flow hydrodynamics. In this in situ study, we made aquatic eddy covariance oxygen flux and profiling acoustic Doppler velocimetry measurements over high and low density sites within an invasive Gracilaria vermi culophylla (also referred to as Agarophyton vermic ulophyllum) macroalgal mat located on a tidal flat along the Virginia (USA) coast. Mean ± SE (n) submerged dark and light oxygen flux over the high density site were −178 ± 9 (144) and 139 ± 26 (104) mmol m −2 d −1 , respectively, vs. −71 ± 7 (45) and 32 ± 15 (48) mmol m −2 d −1 over the low density site. The high density site was highly productive, with gross primary production of 169 ± 12 mmol m −2 d −1 (mean ± SE), yet maintained overall metabolic balance, as net ecosystem metabolism was −22 ± 39 mmol m −2 d −1. Close agreement with literature values for air-exposed flux measurements suggests that our results are good first-order approximations of true daily values, demonstrating that this invasion has significantly enhanced tidal flat productivity. Flow and turbulence were significantly attenuated by Gracilaria, resulting in decreased bed shear stress within the algal canopy, likely stabilizing tidal flat sediments and inhibiting mass transport at the sediment−water interface. Turbulence above the canopy was enhanced, but there was no increase in downward momentum transfer. These changes to the hydrodynamic environment decrease the risk of detachment and subsequent advective loss of algae, suggesting a positive feedback that facilitates algal invasion.

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Oysters are described as estuarine ecosystem engineers because their reef structures provide habitat for a variety of flora and fauna, alter hydrodynamics, and affect sediment composition. To what spatial extent oyster reefs influence surrounding infauna and sediment composition remains uncertain. We sampled sediment and infauna across 8 intertidal mudflats at distances up to 100 m from oyster reefs within coastal bays of Virginia, USA, to determine if distance from reefs and physical site characteristics (reef elevation, local hydrodynamics, and oyster cover) explain the spatial distributions of infauna and sediment. Total infauna density increased with distance away from reefs; however, the opposite was observed for predatory crustaceans (primarily crabs). Our results indicate a halo surrounding the reefs of approximately 40 m (using an increase in ~25% of observance as the halo criterion). At 90 m from reefs, bivalves and gastropods were 70% more likely to be found (probability of observance), while there was an approximate 4-fold decrease for large crustaceans compared to locations adjacent to reefs. Increases in percent oyster reef cover and/or mean reef area did not statistically alter infauna densities but showed a statistical correlation with smaller sediment grain size, increased organic matter, and reduced flow rates. Weaker flow conditions within the surrounding mudflats were also associated with smaller grain sizes and higher organic matter content, suggesting multiple drivers on the spatial distribution of sediment composition. This study emphasizes the complexity of bio-physical couplings and the considerable spatial extent over which oyster reefs engineer intertidal communities.