Thallus Size Research Articles

Local and global stressors as major drivers of the drastic regression of brown macroalgae forests in an oceanic island

Similar to other coastal regions worldwide, forests created by brown macroalgae have severely declined in recent decades across the Macaronesian oceanic archipelagos (northeastern Atlantic), eroding the provision of ecosystem services. However, the putative effects of natural and anthropogenic stressors (both local and global) on such declines across spatial and temporal scales remain unresolved. Our research endeavored to investigate the connection between local and global stressors and the distribution and extent of the brown macroalgae Gongolaria abies-marina in the rocky intertidal and adjacent subtidal zones of Gran Canaria over the past four decades. We also quantified the presence of populations at small scales, according to local micro-habitat topography (“open rock” versus “refuge”). Through herbarium records, we additionally analyzed the historical variation in the thallus size of the species. Finally, we experimentally assessed the thermotolerance of embryonic stages to warming. The main environmental drivers explaining the regression of G.abies-marina were the increasing number of marine heatwaves, while the number of local human impacts (quantified through the HAPI index) also accounted for further regression in the extent of marine forests. Warming experimentally reduced the survival and size of macroalgal embryos. A progressive miniaturization of the species, currently restricted to micro-habitat refuges as a survival strategy, seems likely to be the final stage in the progressive disappearance of this macroalgae from the island’s rocky shores.

Habitat traits and predation interact to drive abundance and body size patterns in associated fauna.

Habitat-forming organisms provide three-dimensional structure that supports abundant and diverse communities. Variation in the morphological traits of habitat formers will therefore likely influence how they facilitate associated communities, either via food and habitat provisioning, or by altering predator-prey interactions. These mechanisms, however, are typically studied in isolation, and thus, we know little of how they interact to affect associated communities. In response to this, we used naturally occurring morphological variability in the alga Sargassum vestitum to create habitat units of distinct morphotypes to test whether variation in the morphological traits (frond size and thallus size) of S. vestitum or the interaction between these traits affects their value as habitat for associated communities in the presence and absence of predation. We found morphological traits did not interact, instead having independent effects on epifauna that were negligible in the absence of predation. However, when predators were present, habitat units with large fronds were found to host significantly lower epifaunal abundances than other morphotypes, suggesting that large frond alga provided low-value refuge from predators. The presence of predators also influenced the size structure of epifaunal communities from habitat units of differing frond size, suggesting that the refuge value of S. vestitum was also related to epifauna body size. This suggests that habitat formers may chiefly structure associated communities by mediating size-selective predation, and not through habitat provisioning. Furthermore, these results also highlight that habitat traits cannot be considered in isolation, for their interaction with biotic processes can have significant implications for associated communities.

Phenology and thallus size in a non-native population of Gracilaria vermiculophylla.

Phenology, or seasonal variation in life cycle events, is poorly described for many macroalgal species. We describe the phenology of a non-native population of Gracilaria vermiculophylla whose thalli are free-living or anchored by decorating polychaetes to tube caps. At a site in South Carolina, USA, we sampled 100 thalli approximately every month from January 2014 to January 2015. We assessed the reproductive state and measured thallus size based on wet weight, thallus length, and thallus surface area from herbarium mounts. Because life cycle stage cannot be assigned using morphology, we implemented a PCR assay to determine the life cycle stage-tetrasporophyte, female gametophyte, or male gametophyte-of each thallus. Tetrasporophytes dominated throughout the year, making up 81%-100% of thalli sampled per month. Reproductive tetrasporophytes varied between 0% and 65% of monthly samples and were most common in warm summer months (July through September) when thalli also tended to be larger. The vast majority of the reproductive thalli were worm-anchored and not fixed to hard substratum via a holdfast. Thus, free-living thalli can be reproductive and potentially seed new non-native populations. Given G. vermiculophylla reproduction seems tied closely to temperature, our work suggests phenology may change with climate-related changes in seawater temperatures. We also highlight the importance of understanding the natural history of macroalgae to better understand the consequence of range expansions on population dynamics.

Growth of Epilithic Lichen under the Conditions of South Karelia

On the territory of the Kivach State Nature Reserve (North-West Russia, the Republic of Karelia) in the supralittoral conditions of the Suna River coast, the growth characteristics of 3 epilithic lichen species – Bellemerea alpina, Lecidea lapicida, Protoparmeliopsis muralis – were studied. Data were analyzed over an 11‑year follow-up period. For each studied thallus, a growth model was created using regression analysis, which reflects the dependence of the area of the thallus on the year of measurement and makes it possible to estimate the age of the thalli. Data were obtained on the size (cm2), growth rate (cm2/year), and age (years) of thalli. For these signs, the confidence interval of the means and the confidence interval of possible values were estimated at a probability of P = 95%.

Ontogenetic Variation in Blade Toughness May Contribute to the Spread of Turbinaria ornata Across the South Pacific.

Coral reefs are shifting from coral to algal-dominated ecosystems worldwide. Recently, Turbinaria ornata, a marine alga native to coral reefs of the South Pacific, has spread in both range and habitat usage. Given dense stands of T. ornata can function as an alternative stable state on coral reefs, it is imperative to understand the factors that underlie its success. We tested the hypothesis that T. ornata demonstrates ontogenetic variation in allocation to anti-herbivore defense, specifically that blade toughness varied nonlinearly with thallus size. We quantified the relationship between T. ornata blade toughness and thallus size for individual thalli within algal stands (N=345) on seven fringing reefs along the north shore of Moorea, French Polynesia. We found that blade toughness was greatest at intermediate sizes that typically form canopies, with overall reduced toughness in both smaller individuals that refuge within the understory and older reproductive individuals that ultimately detach and form floating rafts. We posit this variation in blade toughness reduces herbivory on the thalli that are most exposed to herbivores and may facilitate reproduction in dispersing stages, both of which may aid the proliferation of T. ornata.

Pharmacognostic study of cetraria islandica (L.) Ach. thalli made in Ukraine

The aim was to conduct a pharmacognostic study of C. islandica thalli harvested in Ukraine.
 Material and methods. The study included seven series of C. islandica thalli harvested in Ukraine. Pharmacognostic research was conducted by using generally accepted methods. Quantitative determination of total polyphenols was performed by a spectrophotometric method in terms of pyrogallol and dry raw materials following the requirements of the SPhU 2.0 monograph. The component composition of flavonoid compounds and carboxylic acids was performed by HPLC.
 Results. The pharmacognostic study of 7 series of the C. islandica raw materials was performed. Morphometric parameters were determined, including the fractional composition according to the size of thalli in each series. For the first time, fractions of the mineral and foreign organic matter were separated. The content of mineral foreign matter ranged from 0.22 ± 0.01 % to 2.80 ± 0.12 %; the content of organic foreign matter ranged from 0.15 ± 0.01 % to 2.14 ± 0.11 %. Due to the total foreign matter content, 6 series of the raw materials fulfilled the requirements of the SPhU 2.0 monograph. The accordance of morphological and anatomical description of the series to the requirements of the SPhU 2.0 monograph is shown. New distinctive diagnostic features of the morphological structure were found, namely: coalescence of blades with forming a membrane and branching of cilia along the edge of blades. For the first time for the series of raw materials harvested in Ukraine, the quantitative content of the sum of polyphenols in terms of pyrogallol and dry raw materials was determined, which ranged from 1.21 ± 0.05 % to 1.73 ± 0.04 %. For the first time for C. islandica thalli, the presence of flavonoid compounds: quercetin, luteolin, kaempferol and rutin, and carboxylic acids: sinapic, trans-cinnamic and quinic acids was determined.
 Conclusions. The obtained results can be used as a basis for the relevant sections of the national part of the monograph "Cetraria Iceland" in SPhU 2.0

A new species of Gibsmithia (Dumontiaceae, Rhodophyta) from mesophotic depths of the Papahānaumokuākea Marine National Monument, Hawai‘i, USA

ABSTRACT Molecular phylogenetic analyses of Hawaiian members of the red algal family Dumontiaceae were used to clarify the species diversity of Dudresnaya and Gibsmithia from Hawaiʻi. Although no new species of Dudresnaya were detected in the analyses, D. babbittiana is newly recorded by Lalo, Manawai, and Oʻahu; however, this record remains tentative until the type material is sequenced. A new species of Gibsmithia, G. punonomaewa A.R. Sherwood, is described here and reported from the mesophotic depths (79–104 m) of the Papahānaumokuākea Marine National Monument, Hawaiʻi. This new species differs from all others in the genus based on the following combination of characters: moderate thallus size (up to 11 cm), smooth and terete gelatinous lobes, presence of a stipe (which is often branched), globose carposporangia, and a non-isodiametric shaped cell subtending the tetrasporangia. This new taxon increases the number of Gibsmithia species recorded from Hawaiʻi to three. Phylogenetically, G. punonomaewa is most closely related to G. dotyi (type locality, Lord Howe Island, Australia) and G. larkumii (type locality, One Tree Island, Queensland, Australia), which are both reportedly widespread in distribution. The relatively dark habitat of the mesophotic in Papahānaumokuākea Marine National Monument contrasts with the surface waters of tropical and subtropical habitats where most Gibsmithia species are found, further highlighting the uniqueness of the species.

Systematic revision of the red algal genus Yonagunia (Halymeniaceae, Rhodophyta) from Taiwan, including the description of two new species

ABSTRACT Among the eight species of Yonagunia described in the Indo-Pacific region, five species have been reported from Taiwan. In this study, we re-examined additional herbarium specimens which were morphologically similar to the other Taiwanese species of Yonagunia. Two new species of Yonagunia (Y. robusta sp. nov. and Y. stipitata sp. nov.) were identified based on rbcL sequence analyses, and their vegetative and reproductive structures were documented in detail. Yonagunia robusta is the largest species (up to 13 cm high) found in Taiwan and superficially resembles a previously described species, Y. palmata from northern Taiwan, but the thallus size is much larger and the branches are coarser in Y. robusta. Young plants of Y. stipitata may be confused with Y. maillardii, a species widely distributed in the Indo-Pacific, but the thallus branches are much thinner and numerous reproductive branchlets are formed in clusters in fertile Y. stipitata. Yonagunia robusta is widely distributed from northern to south-eastern Taiwan, whereas Y. stipitata is restricted to Orchid Island, a remote small island off the south-east of Taiwan. The species diversity (seven out of 10 described species) of Yonagunia is high in Taiwan and it is speculated that some more cryptic species will be found from the Indo-Pacific by using a combination of DNA sequence data and morphological observations. HIGHLIGHTS Ten species of Yonagunia have been described from the Indo-Pacific. Seven out of 10 species of Yonagunia are found in Taiwan. Cryptic species of Yonagunia will be found in the Indo-Pacific.

Herbarium macroalgae specimens reveal a rapid reduction of thallus size and reproductive effort related with climate change

Understanding and forecasting the effects of climate changes on vulnerable species are leading concerns for ecologists and conservation biologists. Herbaria are invaluable for use in long-term data series, and one of the few available methods for quantifying biodiversity changes over large periods of time. Gelidium canariense is an endemic and habitat-forming macroalga of the Canary Islands that coexists with two other habitat-forming Gelidiales: G. arbuscula and Pterocladiella capillacea. This study assesses long-term changes in thallus size and reproductive effort of all specimens deposited in the Herbarium of Universidad de La Laguna of these three Gelidiales species. Also assessed were the effects of seawater temperature and increased incident light on net primary production (NPP), and the effects of extreme desiccation conditions on the relative water content and NPP of the three Gelidiales species. The length of the thallus of the endemic species G. canariense was halved during the past 40 years. The shortening of the thallus coincided with a significant decrease in the number of reproductive structures in both Gelidium species. These morphological changes coincide with a significant increase of the sea surface temperature, air temperature above sea surface and ultraviolet radiation in the studied area. The experiments have revealed the deleterious effects of extreme desiccation and extreme irradiance on all three species. Hence, these results suggest that air temperature and irradiance are related with these morphological changes over time in the habitat-forming Gelidium species and that are most likely compromising the survival of their populations which are already declining.

A New Species of Kumanoa (Batrachospermales, Rhodophyta) from Baiyun Mountain, Guangdong, China

Kumanoa belonging to the order Batrachospermales is the most species-rich and widely distributed genus of freshwater red algae in China. In this study, a new Kumanoa species is described and illustrated from Baiyun Mountain, Guangdong, China, based on morphological observations and phylogenetic analysis. Kumanoa baiyunensis sp. nov is morphologically distinguished from other species by presenting a small habit (0.5–1 cm tall) with abundant branching in upper part of the thallus; carposporophytes spherical and one per whorl; club-shaped trichogynes with distinct stalk; spermatangia sparse and single-grown, terminal on primary fascicles. Phylogenetic analysis based on the concatenated rbcL+COI-5P+UPA alignment places Kumanoa baiyunensis in a well-supported clade (98/0.96, bootstrap proportion/posterior probability) sister to K. faroensis (from USA) and K. spermatiophora (from Hawaii) with high divergence (rbcL: 4.9%–5.0%, COI-5P: 10.1%–10.5%, UPA: 2.3%). In addition, K. baiyunensis can be easily distinguished from ten Kumanoa species reported in China through morphological features such as small thallus size, abundant branching in upper parts of the thallus, and spermatangia sparse, single-grown, and terminal on primary fascicles. The description of this new species expands the diversity of genus Kumanoa in the world.

The widely distributed, edible seaweeds in Peru, Chondracanthus chamissoi and Chondracanthus chamissoi f. glomeratus (Gigartinaceae, Rhodophyta), are morphologically diverse but not phylogenetically distinct

AbstractChondracanthus chamissoi is part of the diet of coastal people from Peru and is exported dehydrated to Asian countries for direct consumption. Although it is considered endemic to Peru and Chile, its range has extended to distant regions, such as Korea, Japan, and France. Using morphological and molecular approaches, we examined specimens from Peru assigned to C. chamissoi (including the taxon of uncertain status Chondracanthus glomeratus) to improve phylogenetic and geographical information and characterize its morphological variability. Twenty‐one localities on the Peruvian coast were sampled, obtaining 102 COI and 27 rbcL sequences. To differentiate both entities, morphological characters such as thallus size, consistency, arrangement of main and secondary axes, branching patterns and location of reproductive structures, were analyzed on 46 specimens. While morphological characteristics are clearly contrasting among the two groups, both COI and rbcL phylogenies revealed a well‐supported clade with no genetic differentiation between the two morphologies. Therefore, the phylogenies indicate that C. chamissoi and C. glomeratus form a single taxonomic entity with high morphological variability, large geographic distribution and at least two morphological forms. The smaller form of C. chamissoi can be identified as C. chamissoi f. glomeratus. Such morphological variability can be of interest for future aquaculture development.

Transplant Success of Cladonia perforata (Florida Perforate Cladonia) at the Jupiter Inlet Lighthouse Outstanding Natural Area

At the 120-acre Jupiter Inlet Lighthouse Outstanding Natural Area (ONA) located in southeast Florida, 30 Cladonia perforata thalli were translocated in 2009. Thalli were transplanted from an area with a large C. perforata population, where sand pine fuels had accumulated and were at risk of a fire, to an area that had either been recently burned, or where no fuel treatments were planned in the near future. There was no C. perforata at or near the four transplant recipient locations, which were selected for habitat suitability and their protected locations within the ONA. The four C. perforata recipient sites have been monitored annually since 2009. Across the four transplant locations, C. perforata thalli have increased, numbering 173 in 2015 and 443 in 2020. Based on our findings, translocation of C. perforata was highly successful at the Jupiter Inlet Lighthouse ONA, with an over 14-fold increase in number of individuals in an 11-year period, assisting the colonization of new sites and buffering the lichen's vulnerable population at this location. Larger thallus size, transplant recipient site protection, and site characteristics that facilitated thalli stabilization probably contributed to this success. While habitat conservation of in situ populations is the preferred management practice for species conservation, it is encouraging to know that, with proper methodology and timing, translocation can be a tool for certain species.

A simple test of lichenometric dating using bidecadal growth of Rhizocarpon geographicum agg. and structure-from-motion photogrammetry

Digital photogrammetry was used to measure growth rates and track changes at the margins of marked Rhizocarpon geographicum agg. thalli on quartzite at the Illecillewaet Glacier in western Canada. The decadal rates were used to validate a lichenometric “growth curve” calibrated using the five largest thalli on historically and tree-ring dated surfaces. Macro-photographs of lichens were orthocorrected by ‘Structure from Motion’ (SfM) techniques to create a 20 yr image timeline. Model resolution was high (0.01 to 0.03 mm pix), photo alignment was accurate (mean relative error < 1.4%) and measurements were validated. Mean areal growth in 59 thalli was highly variable (x¯ = 9.43 mm2 yr−1 for 1996–2006; and 7.72 mm2 yr−1 for 2006–2016). Tiny thalli (<5 mm long axis) had jagged outlines and slow irregular growth (0 to 0.2 mm yr−1). Long axis growth in the five fastest of 45 thalli (>5 mm long axis) with circular outlines was 0.5 to 0.92 mm yr−1 and mean annual radial growth on four radii per thallus was 0.23 to 0.31 mm yr−1. Several thalli kept a nearly circular shape even after fusing with others. Extrapolated mean radial growth of the fastest thallus in either decade closely predicted the largest and five thallus sizes on historically dated surfaces (−5.43 mm difference at 53 yr, <1.75 mm at 75 to 101 yr). This is an error of about one year at 75 to 101 yr. The findings validate indirectly calibrated rates and surface ages at this site and challenge key assumptions and claims made by proponents of lichenometric dating.

Molecular phylogenetic analyses reveal two new synonyms of Xanthoria parietina

Molecular analyses of the recently described Xanthoria polessica collected from the type locality and of the Australian species X. coomae were used to determine whether these taxa are distinct species or fall within the wide phenotypic variation of the well-known and cosmopolitan X. parietina. Our results clearly indicate that both taxa should be considered as synonyms of X. parietina since the infraspecific morphological range is accommodated by the observed variation in the thallus and lobe size, their color, position of apothecia, the shape of ascospores, and width of ascospore septum.

Seaweeds through time: Morphological and ecological analysis of Proterozoic and early Paleozoic benthic macroalgae

Benthic marine macroalgae or seaweeds are key ecological players in oceans today and have been since the Proterozoic. To date, however, morphological and evolutionary patterns for Precambrian macroalgae have been documented only in rather broad terms. To refine our understanding in this critical interval, we updated a dataset of Proterozoic to early Paleozoic noncalcified macroalgal fossils preserved as macroscopic carbonaceous compressions. The data were analyzed using non-parametric multidimensional scaling (NMDS) and functional-form group (FFG) approaches, in order to characterize morphological and ecological evolutionary patterns of these macroalgae. At the broadest scale, the results show progressive increases in thallus size, morphospace range, and aspects of ecological complexity such as canopy heights, surface area/volume ratios, and functional-form groups through time. These trends, however, are not always monotonous. In particular, significant increases in Proterozoic macroalgal morphological diversity and maximum size appear to have occurred in the Neoproterozoic (Tonian and Ediacaran periods, respectively). Analysis of Ediacaran macroalgal assemblages shows that macroalgae broadly follow the Ediacara-like fossil assemblages, with a significant drop in most studied metrics in the terminal Ediacaran stage (~550–539 Ma). The latter event occurs during the Kotlinian crisis experienced by Ediacara-type macro-organisms, highlighting the possibility that this extinction event during the Ediacaran-Cambrian transition affected both macroalgae and Ediacara-type macro-organisms. Our analysis also confirms an Ordovician increase in the morphological and ecological diversity of macroalgae.

The cyanolichens Erioderma pedicellatum and Coccocarpia palmicola need much more than a dewfall to fill their water holding capacity

Erioderma pedicellatum, an enigmatic boreal cyanolichen epiphyte is sympatric with the widespread pantropical cyanolichen Coccocarpia palmicola in cool and damp forests in Atlantic parts of Canada. After sampling co-occurring specimens of these lichens in Newfoundland, we quantified important hydration traits. We hypothesized that 1: these lichens restricted to wet forests have higher internal water holding capacity (WHCinternal) than what humid air and dewfall can provide, and 2: the rare E. pedicellatum has higher WHCinternal and / or WHCtotal than the widespread C. palmicola. Both hypotheses were supported: Mean WHCinternal across a wide thallus size range was 0.26 and 0.35 mm H2O in C. palmicola and E. pedicellatum, respectively; corresponding mean WHCtotal were 0.73 and 0.86 mm. These high WHC-levels could only be filled by liquid hydration sources. Because WHC strongly increased with thallus size, larger specimens needed even more water (1.7 mm), emphasizing these species’ dependency on rain and thus wet forests.

Growth Curve of the Crustose Lichen Ochrolechia parella Obtained from Marginal Growth Rings

Thalli of the crustose lichen Ochrolechia parella have marginal ‘growth rings’ enabling rapid estimation of radial growth rates (RaGR) over successive years. I obtained a growth curve, viz. changes in RaGR with thallus size, from rings of two populations of O. parella and in one population, and compared the growth curves obtained from rings and by measuring growth directly. Both methods revealed that RaGR in O. parella increased with thallus size in smaller thalli becoming more constant in larger thalli, a growth curve similar to that of foliose and placodioid species rather than crustose lichens such as Rhizocarpon geographicum in which growth declines in larger thalli. In O. parella the marginal zone comprises a layer of confluent areolae which may be better able to support and maintain a more constant growth rate compared with R. geographicum in which the marginal areolae are often isolated and scattered.

If a Tree Falls in the Forest, Will Its Lichens Flourish or Die?

In 2016, a storm blew over an old growth sand post oak tree (Quercus margarettae) at O'Leno State Park in northern Florida. This event provided access to the entire tree without climbing it. Because the tree was suspended by its branches so it was parallel with the ground, we could easily observe and collect lichens at all former canopy heights. We surveyed the wind-blown tree's lichens before the species' composition changes had occurred. Several uncommon lichens were found on this oak. We rated relative abundance of each lichen species on the tree for three consecutive years. To our surprise, many of the lichens were still alive after one or more years, despite being in a lower canopy position and on a different aspect. However, most lichens changed in relative abundance or were reduced in abundance; one species, Parmeliella triptophylla, increased in relative abundance. Five species did not change, while 26 species decreased in abundance. Lichen response was dynamic in both abundance and thallus size. We found many old growth lichen indicators for Florida and this gave us an opportunity to study rarely encountered lichen species.

Ontogenesis of the Lichen Lobaria pulmonaria (L.) Hoffm. in Plant Communities of the Boreal Zone

The paper describes the ontogenesis of the epiphytic lichen Lobaria pulmonaria. The studies were carried out in the Karelian forest communities with the period since the last disturbance ranging from 80 to 450 years. Based on the concept of a discrete description of plants and lichens, four periods and 14 age-related states have been distinguished in L. pulmonaria’s ontogenesis. Each ontogenetic state of L. pulmonaria is characterized by a certain thallus size as well as by the presence and the level of development of vegetative diaspores and apothecia on the thallus surface. The possible variants of the species ontogenesis are described.

Cell wall thickening in two Ulva species in response to heavy metal marine pollution

The present work was aimed at evaluating the responses of two green algae, Ulva rigida and Ulva intestinalis, to heavy metal pollution in their natural environment. These species were harvested in the Atlantic shorelines of El Jadida (Morocco) at two different stations: first, a non-polluted site (S1) which served as a control, and a second one (S2), which is affected by industrial effluents, mainly from a phosphate facility. Except for iron, the heavy metal concentrations in seawater were higher in station S2 than in station S1 (notably cadmium and lead levels). Consequently, the algal samples collected from S2 presented higher levels of heavy metals compared with those collected in S1. Pollution in station S2 resulted in a reduction in size of thalli of both algal species. Optical microscopy of algal slices showed that the polluted environment induced the thickening of the cell walls along with an enlargement of cell areas. Elevated cell wall yields, higher content of polysaccharides (mainly ulvans), sulfate, and protein were also detected in algae from S2. However, the monosaccharide distribution in cell wall polysaccharides was quite identical in the two species, regardless of the station. Our results describe an adaptation mechanism mainly based on cell wall thickening which restrains the entry of toxic elements into the cells, allowing these algae to enhance their tolerance to heavy metal stress.