Abstract:The seasonally-dry climate of Northern California imposes significant water stress on ecosystems and water resources during the dry summer months. Frequently during summer, the only water inputs occur as non-rainfall water, in the form of fog and dew. However, due to spatially heterogeneous fog interaction within a watershed, estimating fog water fluxes to understand watershed-scale hydrologic effects remains challenging. In this study, we characterized the role of coastal fog, a dominant feature of Northern C… Show more
“…Ocean-facing samples were <1.1 km from the Pacific Ocean whereas the bay-facing group were more spread out, located >24 km from the coast, and averaged 3.7 hrs/day summertime FLCC (Table S1). However, while this FLCC frequency is only 60% less than that for the ocean-facing sites, the difference in summertime fog wet deposition is likely to be at least an order of magnitude, with ocean-facing sites being wetter 21,22 .Figure 1Geographical distributions in the Santa Cruz Mountain coastal region, California, USA, and mean (±1 SE) values by coastal sub-region of ( A ) MMHg concentrations in lace lichen ( Ramalina menziesii ) (site names correspond to data in Table S1), ( B ) THg in adult deer fur, and ( C ) THg in adult puma fur and fur-normalized whisker samples. The blue line represents the watershed boundary which was used to delineate samples as belonging to either the ocean facing (to the left of the line) or bay facing (to the right of the line) sub-regions.…”
Section: Resultsmentioning
confidence: 90%
“…During the months between May and September, coastal locations and ocean-facing ridges are particularly impacted by marine stratus clouds with midday overcast occurring on about 50% of the days 21 . The elevation band between 400 and 500 m experiences the greatest amount of summertime wet deposition 22 . The east side of the range which faces the southern San Francisco Bay receives significantly less marine layer influence and fog drip, even though the wintertime precipitation rates on both sides of the range are similar at locations with similar elevation 21 .…”
Section: Methodsmentioning
confidence: 99%
“…The east side of the range which faces the southern San Francisco Bay receives significantly less marine layer influence and fog drip, even though the wintertime precipitation rates on both sides of the range are similar at locations with similar elevation 21 . Fog water deposition can vary 2–3 orders of magnitude as a result of microclimates, changes in exposure and vegetation type 21,22 . Thus, within the coastal region, a further distinction was made between the ocean-facing and bay- facing sample collection sites, using the summit of the Santa Cruz Mountains as a boundary between these sub-regions.…”
Section: Methodsmentioning
confidence: 99%
“…In coastal zones with consistent periods of onshore advection of marine fog there can be significant wet deposition of fog drip 17–22 . An early study of total Hg in marine fog water in eastern Canada showed that fog water can account for as much as 31–74% of all Hg in wet deposition 23 .…”
Coastal marine atmospheric fog has recently been implicated as a potential source of ocean-derived monomethylmercury (MMHg) to coastal terrestrial ecosystems through the process of sea-to-land advection of foggy air masses followed by wet deposition. This study examined whether pumas (Puma concolor) in coastal central California, USA, and their associated food web, have elevated concentrations of MMHg, which could be indicative of their habitat being in a region that is regularly inundated with marine fog. We found that adult puma fur and fur-normalized whiskers in our marine fog-influenced study region had a mean (±SE) total Hg (THg) (a convenient surrogate for MMHg) concentration of 1544 ± 151 ng g−1 (N = 94), which was three times higher (P < 0.01) than mean THg in comparable samples from inland areas of California (492 ± 119 ng g−1, N = 18). Pumas in California eat primarily black-tailed and/or mule deer (Odocoileus hemionus), and THg in deer fur from the two regions was also significantly different (coastal 28.1 ± 2.9, N = 55, vs. inland 15.5 ± 1.5 ng g−1, N = 40). We suggest that atmospheric deposition of MMHg through fog may be contributing to this pattern, as we also observed significantly higher MMHg concentrations in lace lichen (Ramalina menziesii), a deer food and a bioindicator of atmospheric deposition, at sites with the highest fog frequencies. At these ocean-facing sites, deer samples had significantly higher THg concentrations compared to those from more inland bay-facing sites. Our results suggest that fog-borne MMHg, while likely a small fraction of Hg in all atmospheric deposition, may contribute, disproportionately, to the bioaccumulation of Hg to levels that approach toxicological thresholds in at least one apex predator. As global mercury levels increase, coastal food webs may be at risk to the toxicological effects of increased methylmercury burdens.
“…Ocean-facing samples were <1.1 km from the Pacific Ocean whereas the bay-facing group were more spread out, located >24 km from the coast, and averaged 3.7 hrs/day summertime FLCC (Table S1). However, while this FLCC frequency is only 60% less than that for the ocean-facing sites, the difference in summertime fog wet deposition is likely to be at least an order of magnitude, with ocean-facing sites being wetter 21,22 .Figure 1Geographical distributions in the Santa Cruz Mountain coastal region, California, USA, and mean (±1 SE) values by coastal sub-region of ( A ) MMHg concentrations in lace lichen ( Ramalina menziesii ) (site names correspond to data in Table S1), ( B ) THg in adult deer fur, and ( C ) THg in adult puma fur and fur-normalized whisker samples. The blue line represents the watershed boundary which was used to delineate samples as belonging to either the ocean facing (to the left of the line) or bay facing (to the right of the line) sub-regions.…”
Section: Resultsmentioning
confidence: 90%
“…During the months between May and September, coastal locations and ocean-facing ridges are particularly impacted by marine stratus clouds with midday overcast occurring on about 50% of the days 21 . The elevation band between 400 and 500 m experiences the greatest amount of summertime wet deposition 22 . The east side of the range which faces the southern San Francisco Bay receives significantly less marine layer influence and fog drip, even though the wintertime precipitation rates on both sides of the range are similar at locations with similar elevation 21 .…”
Section: Methodsmentioning
confidence: 99%
“…The east side of the range which faces the southern San Francisco Bay receives significantly less marine layer influence and fog drip, even though the wintertime precipitation rates on both sides of the range are similar at locations with similar elevation 21 . Fog water deposition can vary 2–3 orders of magnitude as a result of microclimates, changes in exposure and vegetation type 21,22 . Thus, within the coastal region, a further distinction was made between the ocean-facing and bay- facing sample collection sites, using the summit of the Santa Cruz Mountains as a boundary between these sub-regions.…”
Section: Methodsmentioning
confidence: 99%
“…In coastal zones with consistent periods of onshore advection of marine fog there can be significant wet deposition of fog drip 17–22 . An early study of total Hg in marine fog water in eastern Canada showed that fog water can account for as much as 31–74% of all Hg in wet deposition 23 .…”
Coastal marine atmospheric fog has recently been implicated as a potential source of ocean-derived monomethylmercury (MMHg) to coastal terrestrial ecosystems through the process of sea-to-land advection of foggy air masses followed by wet deposition. This study examined whether pumas (Puma concolor) in coastal central California, USA, and their associated food web, have elevated concentrations of MMHg, which could be indicative of their habitat being in a region that is regularly inundated with marine fog. We found that adult puma fur and fur-normalized whiskers in our marine fog-influenced study region had a mean (±SE) total Hg (THg) (a convenient surrogate for MMHg) concentration of 1544 ± 151 ng g−1 (N = 94), which was three times higher (P < 0.01) than mean THg in comparable samples from inland areas of California (492 ± 119 ng g−1, N = 18). Pumas in California eat primarily black-tailed and/or mule deer (Odocoileus hemionus), and THg in deer fur from the two regions was also significantly different (coastal 28.1 ± 2.9, N = 55, vs. inland 15.5 ± 1.5 ng g−1, N = 40). We suggest that atmospheric deposition of MMHg through fog may be contributing to this pattern, as we also observed significantly higher MMHg concentrations in lace lichen (Ramalina menziesii), a deer food and a bioindicator of atmospheric deposition, at sites with the highest fog frequencies. At these ocean-facing sites, deer samples had significantly higher THg concentrations compared to those from more inland bay-facing sites. Our results suggest that fog-borne MMHg, while likely a small fraction of Hg in all atmospheric deposition, may contribute, disproportionately, to the bioaccumulation of Hg to levels that approach toxicological thresholds in at least one apex predator. As global mercury levels increase, coastal food webs may be at risk to the toxicological effects of increased methylmercury burdens.
“…The fog induced decrease in VPD reduces evaporative demand, which leads to reduced plant ET. In a San Francisco peninsula watershed, FLCC reduced ET by 25% (Chung et al 2017), in a coastal Atlantic laurel forest by 30% (Ritter et al 2009), and under multi-year drought conditions, the rate could be higher still (Williams et al 2018). Reduced LW reduces ET leaving more water in the subsurface, with the potential for enhanced recharge and baseflow.…”
Section: Hydroclimate Impacts From Fog and Low Cloudsmentioning
Research Impact Statement: Coastal fog and recharge strongly influence late summer instream hydroclimate conditions critical to coho and help to identify watersheds least vulnerable to future warming.ABSTRACT: Fog and low cloud cover (FLCC) and late summer recharge increase stream baseflow and decrease stream temperature during arid Mediterranean climate summers, which benefits salmon especially under climate warming conditions. The potential to discharge cool water to streams during the late summer (hydrologic capacity; HC) furnished by FLCC and recharge were mapped for the 299 subwatersheds ranked Core, Phase 1, or Phase 2 under the National Marine Fisheries Service Recovery Plan that prioritized restoration and threat abatement action for endangered Central California Coast Coho Salmon evolutionarily significant unit. Two spatially continuous gridded datasets were merged to compare HC: average hrs/day FLCC, a new dataset derived from a decade of hourly National Weather Satellite data, and annual average mm recharge from the USGS Basin Characterization Model. Two use-case scenarios provide examples of incorporating FLCC-driven HC indices into long-term recovery planning. The first, a thermal analysis under future climate, projected 65% of the watershed area for 8-19 coho population units as thermally inhospitable under two global climate models and identified several units with high resilience (high HC under the range of projected warming conditions). The second use case investigated HC by subwatershed rank and coho population, and identified three population units with high HC in areas ranked Phase 1 and 2 and low HC in Core. Recovery planning for cold-water fish species would benefit by including FLCC in vulnerability analyses.(
Tropical mountains such as the páramos of the Andes, which serve as ‘water towers’ for local communities and downstream cities, are important areas for early detection of climate change. Here, fog and low‐intensity rainfall are very common and play a key role in ecohydrological processes. Although evapotranspiration (ET) represents an important part of the water cycle, how ET and fog processes interact and how they affect páramo vegetation and water resources availability are poorly understood. This study investigated the effects of foggy (fog only) and mixed (fog and rainfall) conditions on ET. To determine whether fog significantly reduces ET, we compared ET and meteorological data under these two conditions with those during dry days. We found that on foggy days, when fog was most prevalent in the early morning, ET declined on average by 4% and net radiation (Rn) by 9.2%. Under mixed conditions, daily ET declined by 42% and Rn by 33%. In the páramo, where mean annual precipitation and ET are 1210 and 635 mm, respectively, the estimated annual reduction in ET due to fog and rainfall combined is between 77 and 174 mm. We found that during fog and rainfall mixed conditions, solar radiation was reduced, consequently constraining the energy available for ET while sustaining high relative humidity, ultimately reducing water loss. Our findings, which suggest that the presence of fog and low‐intensity rainfall restricts water losses by evaporative demand, contribute to a better understanding of the ecohydrological importance of these water inputs in the Andes.
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