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Effects of the duration of air exposure on (a) leaf desi cation and (b) net photosynthesis of Phyllospadix scouleri an P torreyi. Error bars in (a) represent i 1 SE
Source publication
11 pages, 7 figures, 3 tables. The bathymetric distribution, biomass, growth dynamics and production of surfgrass species in Baja California (NW Mexico) were examined. The maximum cover of Phyllospadix scouleri (16 ± 3.6%) was found between 40 and 50 cm below MLWL (mean low water level), whereas P. torreyi showed continuous cover (100%) at the lowe...
Contexts in source publication
Context 1
... for both spe- cies (Table 2), with area1 leaf production declining more in April, the time of longer air exposure, for P. Phyllospadix torreyi desiccated faster than scouleri in the same environmental conditions, as ev denced by the higher (t-test, t = 2.51, p < 0.05) values the desiccation ratio in the former species after 2 h exposure to air (Fig. 6a). The desiccation of both sur grass species was, however, similar after 3 h of a exposure. Air exposure was detrimental for Table 3. Summary of results of the 2-way ANOVAs performed to test for surfgrass photosynthesis as indicated by sig- the effect of the level of exposure to air on the size of surfgrass shoots. nificant (p < 0.01) ...
Context 2
... by sig- the effect of the level of exposure to air on the size of surfgrass shoots. nificant (p < 0.01) negative slopes of the lin- ' p < 0.05, ' ' p < 0.01, "not significant (p > 0 05) ear regressions between the standardized net photosynthesis rate and the duration of the exposure to air for both species after rehy- dratation of the shoots (Fig. 6b). The slope was more negative (t-test, t = 3.22, p < 0.05) for P, forreyi than for P, scouleri, which indi- cates that the net photosynthesis of P. torreyi was more affected by air exposure than that of P. ...
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Seagrasses are submerged or intertidal angiosperms that form extensive meadows in shallow coastal waters. Tropical as well as temperate seagrass beds are subject to man's interference. Most human activities affect seagrasses either through reductions in light availability or changes in sediment dynamics, the latter often caused by hydrodynamic chan...
Citations
... occurs on wave exposed rocky substrates in the low intertidal and shallow subtidal zones (Hemminga & Duarte, 2000). Inhabiting shallow waters (down to 5 m depth), Phyllospadix species are frequently subjected to sharp environmental fluctuations, particularly intense tidal changes (Ramírez-García et al., 1998). Despite their ability to tolerate substantial tidal environmental variation, such as abrupt exposure to air during tidal fluctuations, these species might thus be close to ecophysiological tolerance limits during such tidal variations, which could render them particularly susceptible to climate-induced range shifts and their effects on genetic diversity along the temperate North Pacific bioregion, as shown for other marine forest-forming species (Grech et al., 2012;Song et al., 2021;Zhang et al., 2019). ...
Aim
Understanding the impacts of past and future climate change on genetic diversity and structure is a current major research gap. We ask whether past range shifts explain the observed genetic diversity of surfgrass species and if future climate change projections anticipate genetic diversity losses. Our study aims to identify regions of long‐term climate suitability with higher and unique seagrass genetic diversity and predict future impacts of climate change on them.
Location
Northeast Pacific.
Time Period
Analyses considered a timeframe from the Last Glacial Maximum (LGM; 20 kybp) until one Representative Concentration Pathway (RCP) scenario of future climate changes (RCP 8.5; 2100).
Major Taxa Studied
Two seagrass species belonging to the genus Phyllospadix.
Methods
We estimated population genetic diversity and structure using 11 polymorphic microsatellite markers. We predicted the distribution of the species for the present, LGM, and near future (RCP 8.5, no climate mitigation) using Species Distribution Models (SDMs).
Results
SDMs revealed southward range shifts during the LGM and potential poleward expansions in the future. Genetic diversity of Phyllospadix torreyi decreases from north to south, but in Phyllospadix scouleri the trend is variable. Phyllospadix scouleri displays signals of genome admixture at the southernmost and northernmost edges of its distribution.
Main Conclusions
The genetic patterns observed in the present reveal the influence of climate‐driven range shifts in the past and suggest further consequences of climate change in the future, with potential loss of unique gene pools. This study also shows that investigating climate links to present genetic information at multiple timescales can establish a historical context for analyses of the future evolutionary history of populations.
... The surfgrass Phyllospadix torreyi S. Watson constitutes large and highly productive (up to ~8000 g DW m-2 year-1) meadows along the Pacific coast of North America, from Vancouver Island (Canada) to Baja California Sur in Mexico (Den Hartog, 1970;Ramıŕez-Garcıá et al., 2002). Since P. torreyi grows in shallow waters (intertidal to ~5 m depth), it is commonly exposed to drastic changes in environmental conditions, such as light, temperature and nutrient availability (Ramírez-García et al., 1998). Although few studies have examined some aspects of its physiology (e.g. ...
This study aimed to elucidate for the first time the combined effects of marine heatwaves (MHWs) and light limitation simulated in mesocosm on critical physiological descriptors of the surfgrass Phyllospadix torreyi, which constitutes highly productive meadows along the intertidal and subtidal rocky shores of the Pacific coast of North America. Our results revealed that short-term exposure (~7 days) to extreme thermal anomalies of +9 °C had positive effects on the photosynthetic capacities of P. torreyi, as indicated by increments in maximum photosynthetic rates, photosynthetic efficiency (α), maximum electron transport rate, and effective quantum yield. Despite that its photosynthetic performance was enhanced, exposure to warming caused a decrease in its internal carbon reserves (i.e. energy status), likely as a consequence of carbon mobilization/utilization to activate heat-stress responses. Plants exposed to light limitation (i.e. sub-saturating irradiance of 30 μmol photon m⁻² s⁻¹) generally exhibited an increase in α and/or a decrease in respiration, which ultimately allowed for a reduction in plant compensation irradiance. The combination of low light and seawater warming resulted in a decrease in non-structural carbohydrates content, daily net-productivity, and leaf growth rates. Gross photosynthetic rates at control saturating irradiance exhibited higher activation energy and, thus, greater responsiveness to seawater warming than plants kept under light limitation. While our results indicated that unusual warming events might favor the photosynthetic performance of P. torreyi, light-limiting conditions can lead to internal carbon depletion and potentially compromise plant survival in the long term.
... Due to its fundamental ecological role, some research has focused on the physiological strategies which Phyllospadix activate to cope with changing environmental conditions (e.g., Craig et al., 2008;Honig et al., 2017), but available knowledge is notably scarce, especially when compared to other seagrass species. Regarding the responses of surfgrasses in the intertidal, Ramírez-García et al. (1998) suggested a vertical zonation of P. scouleri and P. torreyi due to different photosynthetic resistance to desiccation. For its part, Kuo and Stewart (1995) indicated that leaf dehydration on Phyllospadix is very likely to occur because of its thin cuticle, but speculated that this could be ameliorated by leaf overlapping. ...
... For its part, Kuo and Stewart (1995) indicated that leaf dehydration on Phyllospadix is very likely to occur because of its thin cuticle, but speculated that this could be ameliorated by leaf overlapping. Indeed, the elevated shoot density of Phyllospadix (up to ~11000 shoots m − 2 ), together with its high leaf biomass and leaf length (~700 g DW m − 2 and ~70 cm; Ramírez-García et al., 1998), allow these plants to conform mat-like canopies during low tides in which underlying shoots/leaves are protected from desiccation and the incidence of direct solar radiation (see Fig. 1A). Canopy-forming intertidal seaweeds can create microclimatic spaces which strongly conditioned physico-chemical factors and associated organisms (Umanzor et al., 2018). ...
... Phyllospadix torreyi plants were collected on June 2019 from a healthy intertidal meadow growing over a rocky platform located in Ensenada, Mexico (~31 51 ′ 42.9'' N 116 • 39 ′ 23.91'' W). In this shallow meadow, P. torreyi is mixed with Phyllospadix scouleri from the mean watermark to a maximum depth of around 4-5 m (Ramírez-García et al., 1998). Plants were carefully collected in order to maintain their clonal Fig. 1. ...
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.
... These differences could be a result of reproduction, since the composition of sterols is different between the flowering period and other seasons in the seagrass P. torreyi sampled in Southern California (Williams 1995). Ramírez-García et al. (1998) found that P. torreyi from the same region started reproduction in spring and extended over the summer, but had the lowest production of new leaves and biomass in April. Hernández-Carmona et al. (2011) found significant differences in coverage of P. torreyi sampled in the same region, in relation to temperature and nutrient changes associated with El Niño. ...
The seasonal and interannual proximate and sterol composition were assessed in two red (Gelidium robustum, Gelidiaceae and Gracilariopsis sjoestedtii, Gracilariaceae), two brown (Ecklonia arborea, Lessoniaceae and Macrocystis pyrifera, Laminariaceae), and two green (Ulva lactuca and Ulva clathrata, Ulvaceae) macroalgae species and the seagrass Phyllospadix torreyi (Zosteraceae) sampled over 3 years in a subtropical climate in Baja California Sur, Mexico. Each macroalga had a particular sterol composition that was typical of their taxonomic group. The red algae had cholesterol as the major sterol; 92% on average in G. robustum and 90% in G. sjoestedtii, followed by t-dehydrosterol and
brassicasterol. In the brown algae the major sterol was fucosterol, which accounted for approx. 90% and 92% of total sterols for M. pyrifera and E. arborea, respectively,
followed by campesterol (7% and 5%) and isofucosterol (1.5% and 1.3%). The green algae had isofucosterol as the major sterol, with 92% on average for U. lactuca and 87% for
U. clathrata, followed by cholesterol, fucosterol, and brassicasterol or norcholesterol. The seagrass P. torreyi had β-sitosterol as the major sterol (39 to 89%, depending on the season), followed by campesterol (4 to 7%), stigmasterol (3 to 6%), and isofucosterol (1.7 to 3.5%). Four (cholesterol, campesterol, fucosterol, and isofucosterol) of the 14 sterols
identified in macroalgae and the seagrass could be used to differentiate between classes (Florideophyceae – red, Phaeophyceae – brown, Ulvophyceae – green, and Monocots –
seagrass) both seasonally and interannually. The seasonal and interannual sterol composition of macroalgae and seagrass was quite stable, with the exception of red G. sjoestedtii sampled in August and green macroalga U. lactuca and seagrass
P. torreyi both sampled in May 2002. Seasonal and interannual variations of proximate and sterol composition are discussed in relation to their reproductive state and
environmental parameters.
... However, Phyllospadix beds are also slow to recover from physical disturbance (Turner and Lucas 1985;Menge et al. 2005). Like other seagrasses, surfgrasses are highly productive with high leaf turnover rates (Ramirez-Garcia et al. 1998); abundant surfgrass leaves in the form of wrack provide nutrient subsidies for a variety of other ecosystems from the high intertidal to submarine canyons (Green and Short 2003). ...
... It is thought that this trapping of sediment can help create terraces on surf swept shorelines (Gibbs 1902). Lastly, surfgrasses are highly productive plants (Ramirez-Garcia et al. 1998), producing over 8000 g dry weight/m 2 /yr in areas with continuous surfgrass coverage, and annual leaf production rates of 17.8 and 22.6 leaves per shoot for P. torreyi and P. scouleri, respectively (Ramirez-Garcia et al. 1998). Much of this productivity is transported out of surfgrass meadows and provides nutrient subsidies to a variety of other ecosystems (Dugan et al. 2011). ...
... It is thought that this trapping of sediment can help create terraces on surf swept shorelines (Gibbs 1902). Lastly, surfgrasses are highly productive plants (Ramirez-Garcia et al. 1998), producing over 8000 g dry weight/m 2 /yr in areas with continuous surfgrass coverage, and annual leaf production rates of 17.8 and 22.6 leaves per shoot for P. torreyi and P. scouleri, respectively (Ramirez-Garcia et al. 1998). Much of this productivity is transported out of surfgrass meadows and provides nutrient subsidies to a variety of other ecosystems (Dugan et al. 2011). ...
Canada is committed to maintaining biological diversity and productivity in the marine environment under the Oceans Act (Government of Canada 1997). Identifying Ecologically and Biologically Significant Areas (EBSAs) is a key component of this commitment. Fisheries and Oceans (DFO) and the Convention on Biological Diversity (CBD) have developed guidelines and eight combined criteria to identify EBSAs. In 2006, EBSAs were identified in the Northern Shelf Bioregion (NSB) using a two-phase expert-driven approach. In response to a science advice request from Oceans Sector and to address a nearshore geographical gap in the previous process, we assess five nearshore features (canopy-forming kelp forests, eelgrass meadows, estuaries, surfgrass meadows, and high current tidal passages) against the CBD and DFO EBSA criteria. We also summarize the available spatial datasets for each feature, outline feature condition and trends, and note species of particular ecological importance that inhabit the features. Upon assessment of the eight combined DFO and CBD EBSA criteria, there is scientific support to designate canopy-forming kelp forests, eelgrass meadows, and estuaries as nearshore EBSAs. There was insufficient evidence to designate surfgrass meadows as nearshore EBSAs at this time. Similarly, there is not enough spatial or biological information to designate all high tidal current passages in the NSB as nearshore EBSAs. However, three specific high tidal current areas with associated biological information do have strong support for EBSA designation: Hoeya Head Sill, Nakwakto Rapids, and the waters around Stubbs Island. The five features considered here are an initial assessment of nearshore features and are not the only potential nearshore EBSAs in the NSB. Future work in nearshore EBSA identification should consider other nearshore biogenic or physical features against the EBSA criteria such as clam beds, mussel beds, and rocky reefs.
... Surfgrass is susceptible to disturbance (Turner 1985). Surfgrass predominates in the lower intertidal zone and may occur higher up in tidepools (Ramírez-García et al. 1998). ...
Natural Resources Condition Assessment for Cabrillo National Monument in San Diego, California. Purpose of report was to provide park managers an assessment on current conditions, critical data gaps, and selected condition influences for a subset of the Monument's important natural resources.
... In interpreting Fig. 4, it is important to bear in mind the challenges of quantifying resistance and recovery. Fig. 4 is based on the maximum values of three resistance proxies and three recovery measures found in the literature for each genera, normalized against the maximum overall Table S5); B) Rhizome diameter (Duarte, 1991a); C) Shoot weight (Brouns and Heijs, 1986;Duarte, 1991a;Edgar and Robertson, 1992;Ramírez-García et al., 1998); D) Total biomass (Duarte and Chiscano, 1999;Githaiga et al., 2016;Menéndez, 2002;Paling and McComb, 2000); E) Seed density (Kim et al., 2015;Orth et al., 2006b); F) Rhizome extension rate (Duarte, 1991a;Marba and Duarte, 1998;Wortmann et al., 1998); G) Leaf turnover rate (Duarte, 1991a;Vonk et al., 2015); H) Above: below ground biomass ratio (Duarte and Chiscano, 1999;Githaiga et al., 2016). Genera are classified as persistent, colonizing and/or opportunistic as per Kilminster et al. (2015). ...
Seagrass ecosystems are inherently dynamic, responding to environmental change across a range of scales. Habitat requirements of seagrass are well defined, but less is known about their ability to resist disturbance. Specific means of recovery after loss are particularly difficult to quantify. Here we assess the resistance and recovery capacity of 12 seagrass genera. We document four classic trajectories of degradation and recovery for seagrass ecosystems, illustrated with examples from around the world. Recovery can be rapid once conditions improve, but seagrass absence at landscape scales may persist for many decades, perpetuated by feedbacks and/or lack of seed or plant propagules to initiate recovery. It can be difficult to distinguish between slow recovery, recalcitrant degradation, and the need for a window of opportunity to trigger recovery. We propose a framework synthesizing how the spatial and temporal scales of both disturbance and seagrass response affect ecosystem trajectory and hence resilience.
... Phyllospadix forms expansive and dense beds in rocky intertidal and subtidal habitats along the north Pacific coast (den Hartog and Kuo, 2010). Along much of the eastern Pacific, two species, Phyllospadix torreyi and P. scouleri, grow together and occupy both the lower intertidal and upper subtidal zones (Ramirez-Garcia et al., 1998). Both species have broad and almost completely overlapping distributions that span from Baja, California to Alaska (den Hartog, 1970;Phillips, 1979). ...
... Both species have broad and almost completely overlapping distributions that span from Baja, California to Alaska (den Hartog, 1970;Phillips, 1979). While P. torreyi is often found in higher abundances at lower tidal heights due to its sensitivity to air exposure during low tides (Ramirez-Garcia et al., 1998), P. scouleri has been found to coexist with P. torreyi (Ramirez-Garcia et al., 1998;Ramirez-Garcia et al., 2002) and in our study these species were almost always found together at sites and within plots. A third species, P. serrulatus is known to exist in Oregon and Washington (den Hartog, 1970;Phillips, 1979), but was not detected. ...
... Both species have broad and almost completely overlapping distributions that span from Baja, California to Alaska (den Hartog, 1970;Phillips, 1979). While P. torreyi is often found in higher abundances at lower tidal heights due to its sensitivity to air exposure during low tides (Ramirez-Garcia et al., 1998), P. scouleri has been found to coexist with P. torreyi (Ramirez-Garcia et al., 1998;Ramirez-Garcia et al., 2002) and in our study these species were almost always found together at sites and within plots. A third species, P. serrulatus is known to exist in Oregon and Washington (den Hartog, 1970;Phillips, 1979), but was not detected. ...
... Among stressors, such as high and direct light exposure and an increase in temperature, desiccation is regarded as one of the primary factors that determine the intertidal distribution in sessile animals, macroalgae, and seagrasses (Martone et al. 2010, Jiang et al. 2014, Fraser et al. 2016). Many studies have assessed desiccation tolerance in seagrasses and its relation to their intertidal distribution (Leuschner et al. 1998, Ramírez-García et al. 1998, Björk et al. 1999, Tanaka and Nakaoka 2004, Boese et al. 2005, Lan et al. 2005, Shafer et al. 2007, Kahn and Durako 2009, Unsworth et al. 2012, Jiang et al. 2014. Correlations between desiccation tolerance and intertidal distribution of seagrasses have been reported in Phyllospadix torreyi S. Watson and P. scouleri W.J. Hooker (Ramírez-García et al. 1998), Halodule uninervis (Forsskål) Ascherson and Thalassia hemprichii (Ehrenberg) Ascherson (Lan et al. 2005) and Enhalus acoroides (Linnaeus f.) Royle (Unsworth et al. 2012). ...
... Many studies have assessed desiccation tolerance in seagrasses and its relation to their intertidal distribution (Leuschner et al. 1998, Ramírez-García et al. 1998, Björk et al. 1999, Tanaka and Nakaoka 2004, Boese et al. 2005, Lan et al. 2005, Shafer et al. 2007, Kahn and Durako 2009, Unsworth et al. 2012, Jiang et al. 2014. Correlations between desiccation tolerance and intertidal distribution of seagrasses have been reported in Phyllospadix torreyi S. Watson and P. scouleri W.J. Hooker (Ramírez-García et al. 1998), Halodule uninervis (Forsskål) Ascherson and Thalassia hemprichii (Ehrenberg) Ascherson (Lan et al. 2005) and Enhalus acoroides (Linnaeus f.) Royle (Unsworth et al. 2012). Other studies have concluded that desiccation may not be the controlling factor that determines the vertical distribution of seagrasses (eight tropical seagrasses, Björk et al. 1999; Zostera marina Linnaeus and Z. noltii Hornemann, Leuschner et al. 1998;Z. ...
The seagrasses Halophila ovalis and Thalassia hemprichii commonly occur in the upper-intertidal zone where they are subjected to prolonged desiccation during low tides. This study investigated their desiccation tolerance and the mechanisms underlying their eventual recovery. Halophila ovalis exhibited a faster decline in photosynthetic efficiency, measured as effective quantum yield of photosystem II (φPSII), during 90 min of desiccation and did not recover when rehydrated. Thalassia hemprichii, however, showed a nearly full recovery. Desiccation also imposed greater membrane damage on H. ovalis as indicated by a higher electrolyte leakage. In a subsequent experiment, seagrasses were desiccated for 60 min before being rehydrated with seawater containing either chloramphenicol (CMP), cycloheximide (CHX), dithiothreitol (DTT) or no metabolic inhibitor (control). Recovery of φPSII of H. ovalis was hindered by CMP and DTT while CHX had little effect. Recovery of φPSII of T. hemprichii, however, was partially affected by both CMP and CHX to a similar extent and not by DTT. The results indicate that H. ovalis relies substantially on the synthesis of chloroplast-encoded proteins and excess energy dissipation by the xanthophyll cycle whereas T. hemprichii requires limited protein synthesis in both chloroplast and cytoplasm to completely recover their photosynthetic function from desiccation stress.
... Son comunidades muy importantes como productores primarios y refugio de numerosas especies de valor ecológico y comercial de las costas del golfo y caribe la Hydrocharitaceae, y de las costas de Baja California, Baja California Sur y Mar de Cortés la Zosteraceae. De esta última familia sobresalen Zostera marítima por formar, en la zona de Baja California, una de las comunidades más amplias y ecológicamente importantes de pastos marinos (Wyllie-Echeverria y Ackerman, 2003) y las comunidades simpátricas de Phyllospadix scouleri y P. torreyi por la singular adaptación como angiosperma a un hábitat de alta energía en rompientes de la zona intermareal de las costas del pacífico de Baja California y Baja California Sur (Ramírez, et al. 1998a). Del lado del Golfo Thalassia testudinum es la especie más ampliamente distribuida, pero también es posible encontrar a Syringodium filiforme y Halodule wrightii como especies predominantes, ya sea formando manchones puros o más frecuentemente asociaciones de varias especies altamente productivas (Onuf et al. 2003;Short et al. 2007). ...
Los ambientes acuáticos y subacuáticos considerados en el presente capítulo, son aquellos que permiten el desarrollo de plantas vasculares adaptadas a vivir totalmente sumergidas, que emergen del agua o que son tolerantes a la inundación, de manera que su ciclo de vida está estrechamente relacionado con dicho elemento. Se describen los tipos de comunidades y asociaciones que conforman la vegetación acuática y subacuática, resaltando las principales formas biológicas y la composición florística, a partir de dos grandes conjuntos: formaciones leñosas y formaciones herbáceas. Las primeras, son definidas como comunidades con elementos arbóreos y arborescentes dominantes, adaptados a condiciones edáficas de drenaje deficiente, con una tabla de agua fluctuante, que los mantiene semisumergidos la mayor parte del año o al menos, sobre suelo saturado de humedad. El segundo conjunto ilustra la mayoría de las asociaciones de hidrófitas o también llamadas plantas vasculares acuáticas estrictas y que conforman la vegetación sumergida, emergente y flotante de la gran variedad de ecosistemas y hábitats acuáticos distribuidos a lo largo y ancho del territorio nacional, desde el nivel del mar hasta los 3500 m de altitud.
