Saccorhiza Dermatodea Research Articles

Loss, resilience and recovery of kelp forests in a region of rapid ocean warming.

Changes in kelp abundances on regional scales have been highly variable over the past half-century owing to strong effects of local and regional drivers. Here, we assess patterns and dominant environmental variables causing spatial and interspecific variability in kelp persistence and resilience to change in Nova Scotia over the past 40 years. We conducted a survey of macrophyte abundance at 251 sites spanning the Atlantic coast of Nova Scotia from 2019 to 2022. We use this dataset to describe spatial variability in kelp species abundances, compare species occurrences to surveys conducted in 1982 and assess changes in kelp abundance over the past 22 years. We then relate spatial and temporal patterns in abundance and resilience to environmental metrics. Our results show losses of sea urchins and the cold-tolerant kelp species Alaria esculenta, Saccorhiza dermatodea and Agarum clathratum in Nova Scotia since 1982 in favour of the more warm-tolerant kelps Saccharina latissima and Laminaria digitata. Kelp abundances have increased slightly since 2000, and Saccharina latissima and L. digitata are widely abundant in the region today. The highest kelp cover occurs on wave-exposed shores and at sites where temperatures have remained below thresholds for growth (21 °C) and mortality (23 °C). Moreover, kelp has recovered from turf dominance following losses at some sites during a warm period from 2010 to 2012. Our results indicate that dramatic changes in kelp community composition and a loss of sea urchin herbivory as a dominant driver of change in the system have occurred in Nova Scotia over the past 40 years. However, a broad-scale shift to turf-dominance has not occurred, as predicted, and our results suggest that resilience and persistence are still a feature of kelp forests in the region despite rapid warming over the past several decades.

Effects of simultaneous increase in temperature and ocean acidification on biochemical composition and photosynthetic performance of common macroalgae from Kongsfjorden (Svalbard)

Increased temperature and ocean acidification are two main factors threatening Arctic coastal ecosystems. To explore the consequences of increased average temperature and ocean acidification in Kongsfjorden, the performance of six common species of macroalgae, the chlorophyte Monostroma arcticum, the rhodophytes Phycodrys rubens, and Ptilota plumosa, and the phaeophytes Alaria esculenta, Desmarestia aculeata and Saccorhiza dermatodea, was tested after 9 days of culture at 4 and 10 °C in combination with current (ca. 390 ppmv) and future (1000 ppmv) levels of atmospheric CO2 under solar radiation in summer. Temperature affected mainly the photosynthetic performance as measured by PAM fluorescence, particularly the initial slope (α) of ETR curves, the light saturation parameter (E k ), and F v /F m values, as well as the protein content, especially in the phaeophytes. On the other hand, CO2 affected mainly the internal accumulation of carbohydrates and lipids. The C:N balance was largely unaffected. External carbonic anhydrase activity was not inhibited at high CO2, and nitrate reductase activity remained unaffected. The resulting growth rate was not altered by treatments in three out of the six species studied. On the other hand, P. rubens showed a positive effect of increasing temperature, D. aculeata was negatively influenced by CO2, and S. dermatodea was positively affected by CO2. Significant interactions between CO2 and temperature were found in 20 % of the analyses. Whether additive or synergistic, the co-occurrence of a higher temperature with other stressors such as elevated CO2 increases the probability of community changes by modifying the performance of these species.

Species composition, zonation, and biomass of marine benthic macroalgae in Kongsfjorden, Svalbard

Abstract We surveyed macroalgae at Hansneset, Blomstrand (78°39′N, 11°57′E) in Kongsfjorden, Svalbard, down to 30 m depth between 1996 and 1998. In total, 62 species were identified: 16 Chlorophyta, 25 Phaeophyceae, and 21 Rhodophyta. The majority of species (53.5%) belonged to the Arctic cold-temperate group, followed in frequency by species distributed from the Arctic to the warm-temperate region (25.9%). Four endemic Arctic species (Laminaria solidungula, Acrosiphonia flagellata, A. incurva, and Urospora elongata) were found. Two species (Pogotrichum filiforme and Mikrosyphar polysiphoniae) were new to Svalbard. Chlorophyta, Phaeophyceae, and Rhodophyta extended from the eulittoral zone down to 11, 21, and >30 m depths with maximum biomasses at 1–5 m, 5–10 m, and 5–30 m depths, respectively. Annual and pseudoperennial species had highest biomasses in the upper 5 m, while perennials were distributed deeper. The highest biomass (8600 g m-2 wet weight) at 5 m depth comprised mainly L. digitata, Saccorhiza dermatodea, Alaria esculenta, and Saccharina latissima. The biogeographic composition of macroalgae at Hansneset was rather similar to that of northeastern Greenland, but different from that of northern Norway, which has a higher proportion of temperate species. Climate warming and ship traffic may extend some of the distribution ranges of macroalgae from mainland Norway to Svalbard.

UV-susceptibility of zoospores of the brown macroalga Laminaria digitata from Spitsbergen

The UV-susceptibility of zoospores of the lower sublittoral kelp Laminaria digitata was studied in the laboratory under varying fluence of spectral irradiance consisting of photosynthetically active radiation (PAR, 400–700 nm; = P), PAR + UV-A radiation (UV-A, 320–400 nm; = PA), and PAR + UV-A + UV-B radiation (UV-B, 280–320 nm; = PAB). In vivo absorption of phlorotannin, localisation of phlorotannin-containing physodes, structural changes, DNA damage and repair, photosynthesis and germination of zoospores were measured after exposure treatments and after 2–6 days of recovery in dim white light. Photodegradation of phlorotannins was observed after extended exposure to ultraviolet radiation (UVR). The UV-protective function of extra- and intracellular phlorotannins was, therefore, observed only after 8 h, but not after 16-h UVR exposure. The energetic cost of photoprotection may have caused the delay in ontogenic development of zoospores after 8-h exposure to PA and PAB treatment; longer exposure time corresponding to 16-h PA and PAB treatment eventually lead to cell degeneration at 6 days post-cultivation. The formation of cyclobutane–pyrimidine dimers (CPDs), as indicator of DNA damage, was not blocked by the UV-absorbing phlorotannins during the 16-h PAB exposure and the inability for DNA damage repair was likely responsible for low photosynthetic recovery and spore mortality. The higher sensitivity of L. digitata zoospores to UVR compared to other kelps such as Saccorhiza dermatodea and Alaria esculenta confirmed our hypothesis that the depth distribution of adult sporophytes in the field correlates to the sensitivity of their corresponding early life history stages to different stress factors in general and UVR in particular.

Research note: Salinity tolerance of Arctic kelps from Spitsbergen

SUMMARYThe effect of hypo‐ and hypersaline treatments on the effective quantum yield of photosystem II was comparatively studied with a pulse amplitude modulated fluorometer (PAM) in the brown algal speciesAlaria esculenta,Fucus distichus, Laminaria digitata,Laminaria solidungula,Saccharina latissima(formerlyLaminaria saccharina) andSaccorhiza dermatodeacollected in the Arctic Kongsfjorden (Spitsbergen). While the euryhalineF. distichuswas not affected at all by salinities ranging from 5 to 60 psu,A. esculenta, S. latissimaandL. solidungulaexhibited under hyposaline conditions strong loss of pigments (bleaching) or even high mortality reflecting stenohaline features. In contrast to the latter species,L. digitataandS. dermatodeasurvived all salinities, but showed reduced photosynthetic activities at the lowest and highest salt treatments and hence, can be characterized as stenohaline‐euryhaline organisms. The data are discussed in terms of vertical zonation (eulittoral versus sublittoral habitat), in terms of interactive effects with other abiotic factors such as temperature and in terms of the species‐specific acclimation potential.

Impact of ultraviolet radiation on cell structure, UV-absorbing compounds, photosynthesis, DNA damage, and germination in zoospores of Arctic Saccorhiza dermatodea.

Stratospheric ozone depletion leads to enhanced UV-B radiation. Therefore, the capacity of reproductive cells to cope with different spectral irradiance was investigated in the laboratory. Zoospores of the upper sublittoral kelp Saccorhiza dermatodea were exposed to varying fluence of spectral irradiance consisting of photosynthetically active radiation (PAR, 400-700 nm; =P), PAR+UV-A radiation (UV-A, 320-400 nm; =PA), and PAR+UV-A+UV-B radiation (UV-B, 280-320 nm; =PAB). Structural changes, localization of phlorotannin-containing physodes, accumulation of UV-absorbing phlorotannins, and physiological responses of zoospores were measured after exposure treatments as well as after 2-6 d recovery in dim white light (8 mumol photon m(-2) s(-1)). Physodes increased in size under PAB treatment. Extrusion of phlorotannins into the medium and accumulation of physodes was induced not only under UVR treatment but also under PAR. UV-B radiation caused photodestruction indicated by a loss of pigmentation. Photosynthetic efficiency of spores was photoinhibited after 8 h exposure to 22 and 30 mumol photon m(-2) s(-1) of PAR, while supplement of UVR had a significant additional effect on photoinhibition. A relatively low recovery of photosystem II function was observed after 2 d recovery in spores exposed to 1.7 x 10(4) J m(-2) of UV-B, with a germination rate of only 49% of P treatment after 6 d recovery. The amount of UV-B-induced DNA damage measured as cyclobutane-pyrimidine dimers (CPDs) increased with the biologically effective UV-B dose (BED(DNA)). Significant removal of CPDs indicating repair of DNA damage was observed after 2 d in low white light. The protective function of phlorotannins has restricted efficiency for a single cell. Within a plume of zoospores, however, each cell can buffer each other and protect the lower layer of spores from excessive radiation. Exudation of phlorotannins into the water can also reduce the impact of UV-B radiation on UV-sensitive spores. The results of this study showed that the impact of UVR on reproductive cells can be mitigated by protective and repair mechanisms.

Screening capacity of UV-absorbing compounds in spores of Arctic Laminariales

The functional significance of phlorotannins as ultraviolet radiation screens in brown algae is presented. Spectral analysis of zoospore suspensions of the three Arctic Laminariales Saccorhiza dermatodea, Alaria esculenta and Laminaria digitata showed strong absorption in the UV waveband, characteristic of phlorotannins. An induction in the synthesis of the UV-absorbing compound in zoospore suspensions of S. dermatodea and A. esculenta was observed as an increase in absorbance in the UV region after 8 h exposure to the whole light spectrum. Transmission of UVR was also negatively correlated with zoospore density in both these species but not in L. digitata. ‘Biofilters’ constructed from UV-transparent acrylic sheet, containing zoospore suspensions or solutions of phloroglucinol showed varying capacity to protect zoospore cultures from the lethal effects of ultraviolet radiation. Phloroglucinol protects the zoospores from damage by screening out the much harmful shorter UV-B spectra (280–290 nm). Cultured spores of A. esculenta and L. digitata after exposure to the whole light spectrum covered by filters containing phloroglucinol showed high rates of germination, unlike controls covered by seawater-only filters that showed 100% mortality. Biofilters containing zoospore suspensions act as buffers and showed variable UV-protection properties on the germination of its conspecies. At highest zoospore density (∼ 4 × 10 6 spores ml − 1 ), zoospores were observed to screen UV radiation maintaining viability among shielded spores in all species investigated. The protective function of zoospore film is, however, density-dependent in L. digitata. At lower spore density, UV-screening function in S. dermatodea and A. esculenta is attributed to their capacity to accumulate and release UV-absorbing compounds into the medium. Ultraviolet radiation transmission by zoospore suspensions of Saccorhiza and Alaria decreased during exposure to the whole light spectrum which is consistent with the earlier observation of enlarged phenolic vesicles following UVR exposure. The increase in vesicle size and the corresponding increase in UV-absorbing capacity may contribute to greater tolerance of UVR exposure in both species.

Sensitivity and acclimation to UV radiation of zoospores from five species of Laminariales from the Arctic

Spores of five Laminariales from Arctic Spitsbergen were exposed in the laboratory to photosynthetically active radiation (PAR; 400–700 nm), PAR+UVA radiation (UVAR; 320–400 nm) and PAR+UVAR+UVB radiation (UVBR; 280–320 nm). Subsequently, germination was monitored over periods of 3, 6 and 9 days. The investigated species were the upper sublittoral Saccorhiza dermatodea, the upper to mid-sublittoral Alaria esculenta and Laminaria digitata, the mid-sublittoral L. saccharina and the lower sublittoral L. solidungula. The germination capacity decreased sharply after 16 h exposure to PAR+UVAR+UVBR in all species. However, S. dermatodea was able to recover from the damaging effects of UVBR. There was also a small increase in percentage germination of A. esculenta 6–9 days after the treatment. No recovery was evident in the other species. After 8 h exposure to PAR+UVA+UVB, L. digitata recovered completely, and L. saccharina and L. solidungula, partially. The only species susceptible to PAR+UVAR was L. solidungula. One prominent cytological feature of UVR-exposed spores was the enlargement of phenolic vesicles (physodes) (particularly seen in S. dermatodea and A. esculenta), which may have a protective function against UVR. Pilot experiments under natural irradiance conditions indicate that the PAR component of solar radiation exerts an additional stress. Overall the data show that zoospores of the species from the upper sublittoral are less sensitive to UVR or have the capacity to recover from UV stress in contrast to species from deeper waters, probably due to their UV protective and repair capabilities.

Seasonal variation in ecophysiological patterns in macroalgae from an Arctic fjord. II. Pigment accumulation and biochemical defence systems against high light stress

The content of photosynthetic pigments (chlorophyll a, biliproteins, carotenoids) and UV-absorbing mycosporine-like amino acids (MAAs), as well as the activity of reactive oxygen species scavenging enzymes (catalase, superoxide dismutase, glutathione reductase) was investigated in six macroalgal species with respect to the seasonal changes of the solar radiation regime and the macronutrient levels in the seawater of the Kongsfjord (Spitsbergen, Svalbard, Norway). The brown algae Laminaria saccharina, Saccorhiza dermatodea, Desmarestia aculeata; the red algae Palmaria palmata and Devaleraea ramentacea; and one green algal species, Monostroma aff. arcticum, were sampled from the same water depth, before, during and after the break-up of sea ice, first under clear and later under turbid water conditions in late winter, spring and summer 1998. In all species, chlorophyll a (chl a) and total carotenoid content were highest under the sea-ice cover, and decreased gradually upon the sea-ice break-up. Four species showed a subsequent recovery in chl a and total carotenoid concentration in parallel to increasing water turbidity and reduced light availability. In the two red algal species, total phycoerythrin and phycocyanin contents followed a similar trend. Coinciding with the increase in underwater radiation during the sea-ice break-up, both species exhibited a significant increase in the concentration of UV-absorbing MAAs, especially of shinorine and palythine. At the same time, the antioxidative activities of the enzymes superoxide dismutase and catalase in the green and red algae increased, while glutathione reductase activity decreased. Overall, the synthesis of UV-absorbing substances and the increase in the activity of the antioxidative systems in the open-water period imply an increased resistance to high underwater light conditions, including UV radiation. The seasonal changes in pigments and biochemical defence systems may additionally be related to variations in nutrient levels in the seawater. They also reflect the life strategy and the genetic adaptation of the seasonal development to the conditions in the Arctic.

Photosynthetic performance of Arctic macroalgae after transplantation from deep to shallow waters.

Transplantation experiments conducted in the Arctic Kongsfjord (Spitsbergen) in summer 1997 investigated the effects of various types of filtered natural radiation (solar, solar without UV-B, solar without UV-A/B) on photosynthesis of various macroalgae. Two brown algal species (Laminaria solidungula, Saccorhiza dermatodea) and four red algal species (Palmaria palmata, Phycodrys rubens, Phyllophora truncata, Ptilota plumosa) were collected from deeper waters, kept in UV-transparent plexiglass tubes wrapped with different spectral cut-off filter foils and positioned at fixed depths in shallow waters for 7-9days. At regular intervals, chlorophyll fluorescence of photosystem II (optimum quantum yield, F v/F m) was determined, as an indicator of photosynthetic performance. The data demonstrate that shallow-water species such as P. palmata are much less affected by natural photosynthetically active radiation (PAR) and UV radiation near the surface than extremely sensitive deep-water species such as Phyc. rubens which exhibited strong decreases in photosynthetic performance, as well as photobleaching of part of the thallus. The other species showed intermediate response patterns. In most species investigated inhibition of photosynthesis was mainly caused by the UV-B wavelengths. Interpretation of the data clearly indicates species-specific tolerances of photosynthesis to ambient solar radiation which can be explained by broad physiological acclimation potentials and/or genetic adaptation to certain (low or high) irradiances. The species-specific photosynthetic performance under radiation stress is in good accordance with the vertical distribution of the macroalgae on the shore.

Influence of ultraviolet radiation on the growth of the dominant macroalgae of the Barents Sea

Nine species of macroalgae collected on the East Murman coast of the Barents Sea were examined: Laminaria saccharina, Alaria esculenta, Saccorhiza dermatodea, Fucus distichus, Fucus serratus, Fucus vesiculosus (Phaeophyta), Palmaria palmata, Porphyra umbilicalis (Rhodophyta) and Ulvaria obscura (Chlorophyta). The samples were kept in three culturing tanks screened to sequester two wavelength ranges of UV radiation. There was a clear seasonal trend in the influence of UV-A, UV-B and of solar radiation without UV-A+B on the growth of the algae. The maximum growth rate was observed in tests with solar radiation excluding UV radiation. A prominent decrease in growth was induced by UV-B in all the species. Ulvaria obscura appeared to be the most sensitive to in situ levels of UV-B radiation, which reduced its growth rate to 54%. The least sensitivity was recorded in Fucus vesiculosus. There was found to be a critical period in May when the algae are affected most by ultraviolet radiation.

Acclimation of brown algal photosynthesis to ultraviolet radiation in Arctic coastal waters (Spitsbergen, Norway)

In field studies conducted at the Kongsfjord (Spitsbergen) changes of the irradiance in the atmosphere and the sublittoral zone were monitored from the beginning of June until the end of August 1997, to register the minimum and maximum fluxes of ultraviolet and photosynthetically active radiation and to characterise the underwater light climate. Measurements of photosynthesis in three abundant brown algal species (Alaria esculenta, Laminaria saccharina, Saccorhiza dermatodea) were conducted to test whether their photosynthetic performance reflects changing light climate in accordance with depth. Plants sampled at various depths were exposed to controlled fluence rates of photosynthetically active radiation (400–700 nm), UV-A (320–400 nm) and UV-B (280–320 nm). Changes in photosynthetic performance during the treatments were monitored by measuring variable chlorophyll fluorescence of photosystem II. In each species, the degree of inhibition of photosynthesis was related to the original collection depth, i.e. shallow-water isolates were more resistant than plants from deeper waters. The results show that macroalgae acclimate effectively to increasing irradiance levels for both photosynthetically active and ultraviolet radiation. However, the kinetics of acclimation are different within the different species. It is shown that one important strategy to cope with higher irradiance levels in shallow waters is the capability for a faster recovery from high light stress compared to isolates from deeper waters.

Laminarionema elsbetiae gen. et sp. nov. (Ectocarpales, Phaeophyceae), a new endophyte in Laminaria sporophytes

SUMMARYLaminarionema elsbetiae gen. et sp, nov, (Ectocarpaceae, Ectocarpales. Phaeophyceae), a new endophyte of Laminaria japonica Areschoug (Laminariales, Phaeophyceae), is described from Muroran. Hokkaido, Japan. Laminarionema elsbetiae grows in the host tissues forming networks in the epidermal and subcortical layers as well as penetrating into the cortical and medullary layers. Only phaeophycean hairs emerge from the surface of the host tissue. No reproductive cells were found in field material. However, under host‐free culture the species formed three morphologically different reproductive structures. Macrosporangia containing a single large motile spore were formed under long and short day conditions below 20°C, transformed from vegetative cells, conical to elongated in shape, 50–75 μm in length and ca. 10 μm in diameter. Microsporangia were linear to lanceolate, sometimes branched, formed under long and short day conditions below 15°C. Unilocular sporangia were more or less irregular in shape, formed under short day conditions of 5–15°C, 60–75 μm in length and 40–45 μm in diameter. Sexual fusion between macro‐ and microspores was not seen. In mixed cultures of L. elsbetiae with young sporophytes of L Japonica Areschoug as well as Saccorhiza dermatodea (de la Pylaie) J. Agardh, L elsbetiae infected both hosts, grew in the same manner as in natural hosts, and formed macrosporangia between host epidermal cells.

Depth-dependent reproductive output of the green sea urchin, Strongylocentrotus droebachiensis (O.F. Müller), in relation to the nature and availability of food

Reproductive output of green sea urchins ( Strongylocentrotus droebachiensis O.F. Müller) in the field was highest at depths where preferred macro-algae were abundant, and lowest at depths where preferred macro-algae were overgrazed or replaced by non-preferred species ( Agarum and Ptilota). Feeding rate and gonad indices of sea urchins in the laboratory were highest on a diet of preferred algae ( Fucus distichus L. subsp. edentatus (Pyl.) Powell, Laminaria longicruris Pyl., Desmarestia spp. and Saccorhiza dermatodea (Pyl.) J. Ag.), and lowest on the less preferred Agarum cribrosum (Mert.) Bory, Ptilota serrata Kütz., and crustose corallines. Gamete production/unit area in overgrazed habitats was as great or greater than in kelp beds because of the higher biomass of urchins in overgrazed areas. Gonad weight and reproductive output of urchins from habitats poor in food can be increased by providing preferred foods.

Translocation in Saccorhiza dermatodea (Laminariales, Phaeophyceae): anatomy and physiology

An anatomical, ultrastructural, histoautoradiographic, and physiological study was made of the kelp Saccorhiza dermatodea, which possesses an anatomy "atypical" of Laminariales. A freeze-substitution – histoautoradiographic procedure localized 14C-labelled organic matter in highly elongated cells (solenocysts) in the medulla of Saccorhiza. These cells are the major long-distance, symplastic translocation pathway in this alga. Solenocysts are joined to each other via numerous lateral connections involving small intermediary cells called allelocysts. Sieve plates (pore diam: ca. 0.05 μm; pore density: ca. 100 μm−2), pierced by plasmodesmata in which an occasional tubule may be seen, are present at all allelocyst–solenocyst junctions as well as at intercellular connections in the cortex and meristodermal layers. Solenocyst ultrastructure closely resembles that of typical sieve cells of Laminariales. Secondary wall deposition occurs between June and October constricting the numerous lateral sieve plates and nearly occluding the cell lumen; however, no callose plugging was observed in any of the medullary cells. In vivo14C-photoassimilate transport was monitored in S. dermatodea blades using a Geiger–Müller probe. The translocation velocity was estimated at 60–100 mm∙h−1 with a greater translocation rate during the day than at night. Amino acid analyses of the S. dermatodea exudate showed a high alanine and glycine content with maximum concentrations 300 mm above the blade base. Nearly 90% of the 14C activity in both source and sink portions of the blade was in alcohol-soluble matter at the end of 72-h experiments. The unique anatomy of the Saccorhiza blade lends it to experimental exploration of the translocation process in kelp.