Effects of Heat Waves and Light Deprivation on Giant Kelp Juveniles (Macrocystis pyrifera, Laminariales, Phaeophyceae).

Due to climate change, the incidence of marine heat waves (MHWs) has increased, yet their effects on seaweeds are still not well understood. Adult sporophytes of Macrocystis pyrifera, the species forming the iconic giant kelp forests, can be negatively affected by thermal stress and associated environmental factors (e.g., nutrient depletion, light deprivation); however, little is known about the tolerance/vulnerability of juvenile sporophytes. Simultaneously to MHWs, juveniles can be subjected to light limitation for extended periods of time (days-weeks) due to factors causing turbidity, or even because of shading by understory canopy-forming seaweeds. This study evaluated the effects of a simulated MHW (24°C, 7 d) in combination (or not) with light deprivation, on the photosynthetic capacities, nutrient uptake, and tissue composition, as well as oxidative stress descriptors of M. pyrifera juvenile sporophytes (single blade stage, up to 20 cm length). Maximum quantum yield (Fv /Fm ) decreased in juveniles under light at 24°C, likely reflecting some damage on the photosynthetic apparatus or dynamic photoinhibition; however, no other sign of physiological alteration was found in this treatment (i.e., pigments, nutrient reserves and uptake, oxidative stress). Photosynthetic capacities were maintained or even enhanced in plants under light deprivation, likely supported by photoacclimation (pigments increment); by contrast, nitrate uptake and internal storage of carbohydrates were strongly reduced, regardless of temperature. This study indicated that light limitation can be more detrimental to juvenile survival, and therefore recruitment success of M. pyrifera forests, than episodic thermal stress from MHWs.

Marine heatwaves recurrence aggravates thermal stress in the surfgrass Phyllospadix scouleri.

The surfgrass Phyllospadix scouleri grows in highly productive meadows along the Pacific coast of North America. This region has experienced increasingly severe marine heatwaves (MHWs) in recent years. Our study evaluated the impact of consecutive MHWs, simulated in mesocosms, on essential ecophysiological features of P. scouleri. Overall, our findings show that the plants' overall physiological status has been progressively declining. Interestingly, the indicators of physiological stress in photosynthesis only showed up once the initial heat exposure stopped (i.e., during the recovery period). The warming caused increased oxidative damage and a decrease in nitrate uptake rates. However, the levels of non-structural carbohydrates and relative growth rates were not affected. Our findings emphasize the significance of incorporating recovery periods in this type of study as they expose delayed stress responses. Furthermore, experiencing consecutive intense MHWs can harm surfgrasses over time, compromising the health of their meadows and the services they offer to the ecosystem.

SLCO1B1 and SLC10A1 polymorphism and plasma rifampin concentrations in patients with co-morbidity tuberculosis-diabetes mellitus in Baja California, Mexico.

Rifampicin is one of the most important drugs for the treatment of tuberculosis (TB). Polymorphisms in SLCO1B1 and SLC10A1 genes are associated with impaired transporter function of drug compounds such as rifampicin. The relationship between genetic variation, clinical comorbidities, and rifampicin exposures in TB patients has not been completely elucidated. The aim of this study was to investigate the prevalence of SLCO1A1 and SLCO1B1 polymorphisms in TB and TB-DM patients and to determine their relationship with rifampicin pharmacokinetics on patients from México. Blood samples were collected in two hospitals in Baja California, Mexico from February through December 2017. Sampling included 19 patients with TB, 11 with T2DM and 17 healthy individuals. Polymorphisms genotype rs2306283, rs11045818, rs11045819, rs4149056, rs4149057, rs72559746,rs2291075 and rs4603354 of SLCO1B1 and rs4646285 and rs138880008 of SLC10A1 were analyzed by Sanger's sequencing. None of the SLCO1B1 and SLC10A1 variants were significantly associated with rifampicin Cmax. TB and T2DM patients with suboptimal Cmax rifampicin levels showed wild alleles in rs11045819 and rs2291075 in SLCO1B1 SLC10A1 and SLC10A1. This is the first study to analyze SLC10A1 and SLCO1B1 polymorphisms in TB and TB-T2DM patients and healthy individuals in Mexico. Further research to confirm and extend these findings is necessary.

Ecophysiological responses and self-protective canopy effects of surfgrass (Phyllospadix torreyi) in the intertidal.

Intertidal seagrasses are subjected to desiccation and direct solar radiation during low tides. It is assumed that the canopy structure can self-protect the underlying shoots during these events, although there is no evidence on a physiological basis. The physiological responses of the surfgrass Phyllospadix torreyi were examined when emerged during low tide, on i) shoots overlaying the canopy, and ii) shoots sheltered within the canopy. Leaf water potential and water content decreased in external leaves after emersion, and the higher concentration of organic osmolytes reflected osmoregulation. Additionally, these shoots also exhibited a drastic reduction in carbohydrates after re-immersion, likely from cellular damage. Lipid peroxidation and antioxidant activity increments were also detected, while photosynthetic efficiency strongly diminished from direct exposure to solar radiation. Conversely, the sheltered shoots did not dehydrate and solely accumulated some oxidative stress, likely resulting from the warming of the canopy. In conclusion, the leaf canopy structure buffers physiological stress in the sheltered shoots, thus acting as a self-protective mechanism to cope with emersion.

The Structure of Genetic Diversity in Eelgrass (Zostera marina L.) along the North Pacific and Bering Sea Coasts of Alaska.

Eelgrass (Zostera marina) populations occupying coastal waters of Alaska are separated by a peninsula and island archipelago into two Large Marine Ecosystems (LMEs). From populations in both LMEs, we characterize genetic diversity, population structure, and polarity in gene flow using nuclear microsatellite fragment and chloroplast and nuclear sequence data. An inverse relationship between genetic diversity and latitude was observed (heterozygosity: R2 = 0.738, P < 0.001; allelic richness: R2 = 0.327, P = 0.047), as was significant genetic partitioning across most sampling sites (θ = 0.302, P < 0.0001). Variance in allele frequency was significantly partitioned by region only in cases when a population geographically in the Gulf of Alaska LME (Kinzarof Lagoon) was instead included with populations in the Eastern Bering Sea LME (θp = 0.128-0.172; P < 0.003), suggesting gene flow between the two LMEs in this region. Gene flow among locales was rarely symmetrical, with notable exceptions generally following net coastal ocean current direction. Genetic data failed to support recent proposals that multiple Zostera species (i.e. Z. japonica and Z. angustifolia) are codistributed with Z. marina in Alaska. Comparative analyses also failed to support the hypothesis that eelgrass populations in the North Atlantic derived from eelgrass retained in northeastern Pacific Last Glacial Maximum refugia. These data suggest northeastern Pacific populations are derived from populations expanding northward from temperate populations following climate amelioration at the terminus of the last Pleistocene glaciation.

Population genetic structure of annual and perennial populations of Zostera marina L. along the Pacific coast of Baja California and the Gulf of California.

The Baja California peninsula represents a biogeographical boundary contributing to regional differentiation among populations of marine animals. We investigated the genetic characteristics of perennial and annual populations of the marine angiosperm, Zostera marina, along the Pacific coast of Baja California and in the Gulf of California, respectively. Populations of Z. marina from five coastal lagoons along the Pacific coast and four sites in the Gulf of California were studied using nine microsatellite loci. Analyses of variance revealed significant interregional differentiation, but no subregional differentiation. Significant spatial differentiation, assessed using theta(ST) values, was observed among all populations within the two regions. Z. marina populations along the Pacific coast are separated by more than 220 km and had the greatest theta(ST) (0.13-0.28) values, suggesting restricted gene flow. In contrast, lower but still significant genetic differentiation was observed among populations within the Gulf of California (theta(ST) = 0.04-0.18), even though populations are separated by more than 250 km. This suggests higher levels of gene flow among Gulf of California populations relative to Pacific coast populations. Direction of gene flow was predominantly southward among Pacific coast populations, whereas no dominant polarity in the Gulf of California populations was observed. The test for isolation by distance (IBD) showed a significant correlation between genetic and geographical distances in Gulf of California populations, but not in Pacific coast populations, perhaps because of shifts in currents during El Niño Southern Oscillation (ENSO) events along the Pacific coast.