Volume 51, Issue 2

We used aerial photography and GIS to establish a quantitative baseline of propeller and off-road vehicle (ORV) scarring in seagrass and wind-tidal flats of the upper Laguna Madre in the Padre Island National Seashore (Texas, USA). We also examined scar recovery through comparison of recent (2002, 2005) and historical (1967) aerial photographs of the study area. Scarring intensity was calculated using two different methods. In the first, polygons were visually drawn around groups of scars on digital images. Scarring intensity was estimated as light (<5%), moderate (5–20%), or severe (>20%), based on the total coverage of scars within each polygon (taking into account the length, width, and density of scars). We developed a more objective method that employed creation of vector grid cells and buffers that incorporated the localized ecological impact of scars. Results of spatial and temporal analysis revealed that the polygon approach greatly underestimated the magnitude of scarring. For example, in a single photograph, 7% of seagrass area was lightly scarred according to the polygon method; but light scarring increased to 51% according to grid analysis of the same image. Our results also indicated that propeller scars in Halodule wrightii beds appear to recover in less than three years and ORV tracks have persisted in the wind-tidal flats for at least 38 years. Our approach provides resource managers with procedures for a more objective and efficient assessment of physical disturbances to seagrass and wind-tidal flats caused by boats and ORVs.

The seasonal variation in biometric and biomass features of a deep subtidal Zostera marina bed (depth 12–14 m) in Cañuelo Bay (southern Spain) was studied through an annual cycle. Shoot density was greatest in September 2004 (402.4±22.01 shoots m -2 ) and lowest in March 2005 (220.8±51.2 shoots m -2 ). Shoots with inflorescences were only observed in June 2004, with up to 9.6 fertile shoots m -2 . Mean shoot height, leaf width and leaf area index also varied seasonally, with maximum values in June–September and minimum values in December– March. The above-ground (leaf) biomass also varied seasonally, with maximum values in June–September (90–100 g dw m -2 ) and minimum values in March 2005 (8.4±2.7 g dw m -2 ). The below-ground (rhizome) biomass remained very stable (90–100 g dw m -2 ) throughout the year. The deep Z. marina bed in Cañuelo Bay had a similar, but less pronounced, seasonal pattern compared to that observed in shallower beds in temperate areas of the Northern Hemisphere. The rather low attenuation coefficient and stable temperature (14–21°C) of the water column throughout the year may favour the development of eelgrass beds at this depth and in this part of the distribution range.

Bacterial communities in sediments engage in activities that determine the pathways and rates of organic matter remineralization. Changes in bacterial community composition might result in greater restoration success if interactions among seagrasses, sediment, and bacterial communities were elucidated. A manipulative experiment that disrupted the sediment bacterial community examined the response of Thalassia testudinum transplants. Planting units were transported to a suitable location and replanted with either autoclaved, transplant, or donor site sediments. Sediments from the rhizosphere were sub-sampled for analysis of the 16S rDNA gene. The autoclave treatment group had significantly lower bacterial diversity than the other treatments, as measured with terminal restriction fragment length polymorphism. Significantly higher mortality of the transplants was observed in the autoclave treatment group, while mortality in the donor and transplant treatment groups was low relative to the control group. Rhizosphere disruption through the removal of surrounding sediments did not increase mortality, while manipulating the composition of the bacterial community increased mortality in transplants. A native bacterial community was a critical component for minimizing short-term stress associated with a seagrass transplant, which suggests a tighter coupling between seagrasses and sediment bacterial communities than previously thought.

Species composition and seasonal changes in macroalgal blooms in six coastal lagoons highly impacted by human activities were tracked for the three seasons between May 2004 and April 2005. Though temperatures were lower during the cold season than during the dry and rainy seasons and some locations showed variations in salinity during the rainy season, nutrient concentrations showed no defined pattern and varied according to season and location. A total of 10 seaweed species and the cyanobacterium Microcoleus lyngbyaceus had biomasses >1 g m -2 dry weight, but only four species represented >1% of the annual biomass. During the dry season, Spyridia filamentosa had the highest biomass (57.5 g m -2 ). During the rainy season, Gracilaria vermiculophylla was the most conspicuous and abundant species (64.0–291.0 g m -2 ) and during the cold season, Caulerpa sertularioides had the highest biomass (180.1 g m -2 ). Abundances of these species were higher than previously reported for this region. Correlation analyses showed a positive correlation between total phosphorus and the biomass of G. vermiculophylla , suggesting that this nutrient might be limiting its growth. C. sertularioides abundance had a positive correlation with N:P ratios, suggesting that high concentrations of nitrogen relative to low phosphorus levels favor its growth. These analyses revealed that nutrient concentrations are most likely to affect macroalgal growth, but temperature and salinity also play a role. This information may be useful for monitoring future blooms and determining changes over time.

Growth, external morphology and reproductive phenology of a southern Adriatic population of Pterocladiella capillacea from a marine cave were investigated. Production of new uprights from creeping axes was limited to late autumn–winter; upright growth in length and branching order increase reached their maxima in late summer. Tetrasporic fronds were dominant from June to September, with a peak in July, while cystocarpic uprights were rather rare and recorded in August only. Two stable, distinct morphotypes occurred in this population at two sampling sites exposed to different daily photon irradiances. Uprights from the more illuminated site were regularly pinnate, with numerous closely packed lateral branches, representing the best-known phenotype of the species; in contrast, uprights from the more shaded inner site had very long and narrow axes, greater intervals between first-order branches and lower branching order. Statistical analysis demonstrated that upright growth in length and branching was significantly different at the two sites; upright biomass in the more illuminated site was generally higher because of the higher orders of branching.

Although it has been suggested that the distribution of Dictyota dichotoma is probably restricted to the European Atlantic Ocean and the Mediterranean Sea, its occurrence in the Canary Islands (new southernmost distribution limit) is confirmed by nuclear ribosomal sequence data (LSU rDNA). Even though D. dichotoma has been described and illustrated prominently in early studies of brown algae, the species remains difficult to characterize due to considerable morphological plasticity. An exhaustive analysis of several quantitative characters confirms significant morphological variation both seasonally and between life-cycle phases. The species may be characterized in the Canary Islands only by the following qualitative features: erect thallus attached by a single holdfast, subdichotomous branches always of similar width, straight terminal segments and smooth margins and an entirely unilayered medulla. In the Canary Islands, D. dichotoma is an aseasonal annual with at least three overlapping generations in which sporophytes and gametophytes grow simultaneously. Thallus life span seems to be less than 3 months. The species occurs throughout the year, but as cryptic microthalli in autumn. Two abundance peaks were detected with the maximum value in February (6.2 thalli m -2 ). The optimum reproductive stage (88.3% fertile specimens) occurred in winter and the maximum vegetative stage (maximum thallus length: 18.6 cm) in summer. Sporophytes outnumbered gametophytes throughout the year, with ratios decreasing from 13.2±1.1 in winter to 1.9±0.2 in summer. Gametophytes made up to 25% of the population and fertile thalli were always dominant. The populations from the Canaries exhibited a temporal displacement compared to northern populations with the favorable period in the coldest season (winter) and the resting period in the warmest season (autumn).

A new species, Chylocladia wynnei sp. nov., is described from the Mediterranean Sea. It consists of 2–4 terete, unbranched erect axes, 5–10(–13) mm high, arising from a discoid holdfast. Axes, covered by a thick mucilaginous layer, are hollow throughout. They are divided into segments by monostromatic diaphragms and are constricted at the diaphragms. Axes have a unilayered cortex and longitudinal filaments lining their inner surface; gland cells are cut off from these filaments. Gametophytic plants are dioecious and consist of only two segments. Male thalli have spermatangia in superficial sori located between the two segments. One or two spherical sessile cystocarps are borne on the distal part of the basal segment. Tetrasporic plants comprise 4–5 segments; tetrahedrally divided tetrasporangia are scattered throughout the thallus. These sporangia are transformed from larger cortical cells and, when mature, they protrude into the thallus cavity. Diminutive stature and unbranched erect axes covered with a thick mucilaginous layer clearly distinguish C. wynnei from previously described species of Chylocladia .

A new species of the genus Diplopsalopsis , D. kisselevii sp. nov., was found in Amursky Bay off the northwestern coast of the Sea of Japan. This species combines the Diplopsalopsis plate pattern with a protoperidinoid shape. The plate tabulation is Po, X, 3′, 2a, 7″, 4c, 4s, 5′″, 2″″. Cells are oval or almost rounded, slightly longer than wide and slightly flattened dorso-ventrally, 34–48 μm long and 34–46 μm wide. The length/width ratio is 1.0–1.05. The epitheca is slightly shorter than the hypotheca. The cingular list is very narrow, smooth and without ribs. The left sulcal list is narrow and short. The apical sunken depression of the theca contains the comma-like pore complex. Two intercalary plates are present. The narrow, long and hexagonal 1a contacts the 2′, 1″, 2″, 3″, 4″, and 2a plates. The large pentagonal 2a is positioned on the dorsal side of the epitheca with no contact to the Po plate. Diplopsalopsis kisselevii sp. nov. is similar to D. latipeltata in cell shape, and possesses reduced cingular and left sulcal lists and a long intercalary plate. However, D. kisselevii can be differentiated from D. latipeltata by the structure of the theca, the tabulation formula of the epitheca, and the shape, size and position of the anterior intercalary 1a plate.

Laurencia caduciramulosa is recorded for the first time for the eastern Atlantic Ocean off Tenerife, Canary Islands, Spain. The specimens were collected in 2006, growing epilithically in the lower intertidal zone on moderately exposed rocky shores. This species is characterized by reduced size, a well-developed stolon-like basal system and erect axes with abundant deciduous branchlets that function as propagules, except on the uppermost portions of the branches, where they form crowns of branchlets. As in all other reports of this species, gametangia and sporangia were not observed. This study expands the geographical distribution of L. caduciramulosa to the eastern Atlantic Ocean.