Nabeta Bay Research Articles

A new species of the genus Rhinoecetes Just, 1983 (Crustacea: Amphipoda: Ischyroceridae) from Japan

A new species of ischyrocerid amphipods, Rhinoecetes spinicaudus sp. nov., is described from Nabeta Bay, southeast coast of Izu Peninsula, central Japan. This new species can be distinguished from the other congeners by the presence of spinulation on the lateral margins of uropod I rami, row of small robust setae on uropod II ramus, and single robust seta on uropod III ramus. More detailed distinguishing characters from R. albomaculosus are also discussed. This is the first record of the genus Rhinoecetes from Japan. Key to all the species of Rhinoecetes is provided.

New species of Trophoniella from Shimoda, Japan (Annelida, Flabelligeridae).

Trophoniella hephaistos sp. n. was collected from a tank irrigated with seawater pumped directly from Nabeta Bay, Japan. This species is discriminated from other Trophoniella by having dorsal tubercles, a tongue-shaped branchial plate, a tunic covered with large sediment grains dorsally and ventrally, having eyes, and anchylosed neurohooks starting from chaetigers 17–20. This is the first record of Trophoniella from Japanese waters. Identification keys to species of Trophoniella and four gene sequences (COI, 16S, 18S, 28S) of this species are provided. Phylogenetic analysis was conducted to clarify phylogenetic position of Trophoniella in Flabelligeridae using four genes.

Identification of a novel carotenoid, 2'-isopentenylsaproxanthin, by Jejuia pallidilutea strain 11shimoA1 and its increased production under alkaline condition.

Carotenoids are a class of naturally occurring pigment, carrying out important biological functions in photosynthesis and involved in environmental responses including nutrition in organisms. Saproxanthin and myxol, which have monocyclic carotenoids with a γ-carotene skeleton, have been reported to show a stronger antioxidant activity than those with β-carotene and zeaxanthin. In this research, a yellow-orange bacterium of strain 11shimoA1 (JCM19538) was isolated from a seaweed collected at Nabeta Bay (Shizuoka, Japan). The 16S rRNA gene sequence of strain 11shimoA1 revealed more than 99.99 % similarity with those of Jejuia pallidilutea strains in the family Flavobacteriaceae. Strain 11shimoA1 synthesized two types of carotenoids. One of them was (3R, 3'R)-zeaxanthin with dicyclic structure and another was identified as (3R, 2'S)-2'-isopentenylsaproxanthin, a novel monocyclic carotenoid with pentenyl residue at C-2' position of saproxanthin, using FAB-MS, (1)H NMR, and CD analyses. Culturing strain 11shimoA1 in an alkaline medium at pH 9.2 resulted in a markedly increased in production of 2'-isopentenylsaproxanthin per dry cell weight, but a decreased in zeaxanthin production as compared to their respective production levels in medium with pH 7.0. These carotenoids are likely to play some roles in the adaptation of the bacterium to the environmental conditions.

Connecting the dots: confirmation and description of Paranamixis misakiensis Thomas, 1997 leucomorphs (Amphipoda, Leucothoidae)

Leucothoid amphipods in the genus Paranamixis Schellenberg, 1938 exhibit two morphologies: pre-transformational leucomorphs and post-transformational anamorphs. The previously unknown leucomorph stage of Paranamixis misakiensis Thomas, 1997 is described. The connection of the leucomorph lifestage to the anamorph lifestage is confirmed via collection from a sponge host in Nabeta Bay, Shimoda, Izu Peninsula, Japan and with nuclear 18S ribosomal DNA sequences.

Photosynthetic performance of transplanted ecotypes of Ecklonia cava (Laminariales, Phaeophyta)

Young sporophytes of short-stipe ecotype of Ecklonia cava from a warmer locality (Tei, Kochi Pref., southern Japan) and those of long-stipe ecotype from a cooler locality (Nabeta, Shizuoka Pref., central Japan) were transplanted in 1995 to artificial reefs immersed at the habitat of long-stipe ecotype in Nabeta Bay, Shizuoka Pref., central Japan. The characteristics of photosynthesis and respiration of bladelets of the transplanted sporophytes of the two ecotypes were compared in winter and summer 1997; the results were assessed per unit area, per unit chlorophyll a content and per unit dry weight. In photosynthesis-light curves at 10‐29 ◦ C, light saturation occurred at 200‐400 µmol photon m ‐2 s ‐1 in sporophytes from both Tei and Nabeta. The maximum photosynthetic rate (Pmax )a t10‐29 ◦ C and the light-saturation index (Ik )a t25‐29 ◦ Ci nsporophytes from both localities were generally higher in winter than in summer. Pmax at 25‐29 ◦ C (per unit area and chlorophyll a) were higher in sporophytes from Tei than those from Nabeta in both seasons. The optimum temperature for photosynthesis was 25 ◦ Ci nwinter and 27 ◦ Ci nsummer at high light intensities of 100‐400 µmol photon m ‐2 s ‐1 .H owever, at lower light intensities of 12.5‐50 µmol photon m ‐2 s ‐1 ,i t was 20 ◦ Ci nwinter and 25‐27 ◦ C in summer for sporophytes from both locations. Dark respiration increased with temperature rise in the range of 10‐29 ◦ Ci nsporophytes from both locations in summer and winter. The sporophytes transplanted from Tei (warmer area) showed higher photosynthetic activities than those from Nabeta (cooler area) at warmer temperatures even under the same environmental conditions. This indicates that these physiological ecotypes have arisen from genetic differentiation.

Dark respiration of the stipe of Ecklonia cava (Laminariales, Phaeophyta) in relation to temperature

SUMMARY Sporophytes of Ecklonia cava Kjellman (Laminariales, Phaeophyta) with a stipe length of 22‐102 cm were collected at 6‐9 m depth in Nabeta Bay, Shimoda, central Japan by scuba diving in February (winter) and in August (summer) 1998. Dark respiration of the intact stipe of E. cava was measured at various water temperatures ranging from 15 to 27.5 ° C in winter and 15‐30 ° C in summer in a closed system by using a dissolved oxygen meter. The stipe respiration was compared on whole stipe, length, surface area, volume, wet weight and dry weight bases. On each basis, the stipe respiration always increased with a rise in water temperature within the temperature range investigated. The stipes showed similar respiration rates on each basis of length, surface area, volume, wet weight and dry weight at each temperature, irrespective of the stipe length. The mean respiration rates in winter (at 15‐27.5 ° C) were: length, 16.7‐32.5 µ L O 2 cm ‐1 h ‐1 ; surface area, 3.2‐6.2 µ L O 2 cm ‐2 h ‐1 ; volume, 7.6‐15.0 µ L O 2 cm ‐3 h ‐1 ; wet weight, 6.2‐12.2 µ L O 2 g (wet weight) ‐1 h ‐1 ; and dry weight, 43.8‐88.0 µ L O 2 g (dry weight) ‐1 h ‐1 . Those for summer (at 15‐30 ° C) were: length, 17.1‐32.0 µ L O 2 cm ‐1 h ‐1 ; surface area, 3.6‐6.8 µ L O 2 cm ‐2 h ‐1 ; volume, 9.7‐18.7 µ L O 2 cm ‐3 h ‐1 ; wet weight, 7.6‐14.6 µ L O 2 g (wet weight) ‐1 h ‐1 ; and dry weight, 49.4‐95.8 µ L O 2 g (dry weight) ‐1 h ‐1 . This is the first report of the intact stipe respiration of E. cava at various temperatures.

Relationships Between Age and Morphology of Ecklonia cava (Laminariales, Phaeophyta) Sporophytes Growing in Nabeta Bay, Shimoda, Southern Izu Peninsula, Japan

Relationships Between Age and Morphology of Ecklonia cava (Laminariales, Phaeophyta) Sporophytes Growing in Nabeta Bay, Shimoda, Southern Izu Peninsula, Japan

Growth and survival rates of large-type sporophytes of Ecklonia cava transplanted to a growth environment with small-type sporophytes

Stipe lengths of sporophytes of Ecklonia cava Kjellman have been reported to be longer along the southeast than southwest coast of the Izu Peninsula, central Japan. Two bays in this region that have natural populations of E. cava, but with different stipe lengths, were chosen for transplant experiments to examine if stipe length was an environmentally controlled trait. Transplant experiments were carried out in order to determine whether large-type sporophytes of E. cava with long stipes growing in Nabeta Bay (southeast Izu Peninsula, Japan) would turn into small-type sporophytes with short stipes when transplanted to Nakagi Bay (southwest Izu Peninsula). Ten juvenile sporophytes of E. cava (stipe length < 5 cm) were collected from Nabeta Bay (large-type habitat) and transplanted to Nakagi Bay (short-type habitat) in December 1995. As a transplant control, ten juvenile sporophytes of E. cava growing in Nakagi Bay were also transplanted to the same artificial reefs. Growth and survival rates of the sporophytes were monitored monthly for 3 y until December 1998. The transplanted sporophytes showed an increase in their stipe length and diameter from winter to spring, whereas almost no increase was observed from summer to autumn. However, the elongation was greater in Nabeta sporophytes than in Nakagi sporophytes. The primary blade length increased mainly from winter to early spring and decreased largely in autumn. Average primary blade lengths were similar in both Nabeta and Nakagi sporophytes from the end of the first year of transplanting. Although ca. 70% of both Nabeta and Nakagi sporophytes survived during the first 2 y after transplantation, no Nakagi sporophytes and only two Nabeta sporophytes survived to the end of the 3 y study period. Despite transplantation to Nakagi Bay, where short sitpes are naturally present, the sporophytes from Nabeta Bay persisted in having longer stipes, which suggests that stipe length is genetically, rather than environmentally, controlled.

Growth of Ecklonia cava (Laminariales, Phaeophyta) sporophytes transplanted to a locality with different temperature conditions

SUMMARY Transplanting experiments were carried out to determine whether the small type sporophytes with short stipe of Ecklonia cava Kjellman (Laminariales, Phaeophyta) growing in a locality with warm temperatures, change into larger type with a long stipe when transplanted to a locality with cooler temperatures. Juvenile E. cava sporophytes, having a stipe shorter than 5 cm long were collected from Tei in Tosa Bay (southern Japan) (seawater temperature 15–29°C) and transplanted to Nabeta Bay (central Japan) (seawater temperature 13–25°C), where larger type E. cava sporophytes characterized by long stipe (ca 1 m) grow. They were attached to artificial reefs at the sea bottom (9 m depth) in Nabeta Bay to monitor their growth. For comparison, juvenile E. cava sporophytes of almost similar size growing in Nabeta Bay were also transplanted in the same way to the same experimental site. Observations of growth of sporophytes from Tei and Nabeta were carried out monthly for 2 years from November 1995 to October 1997. The transplanted Tei and Nabeta sporophytes showed an increase in stipe length and diameter from winter to spring, whereas almost no increase was observed during summer and autumn. At the end of the study period, the stipe of Nabeta sporophytes reached 25.6 cm in length and 17.0 mm in diameter, whereas that of Tei sporophytes reached 11.1 cm in length and 11.2 mm in diameter. The primary blade length was 16.0 cm in Nabeta sporophytes, whereas it was 5.5 cm in Tei sporophytes. Thus, Tei sporophytes still remained smaller than Nabeta sporophytes even under the same environmental conditions.

Morphometric study of Ecklonia cava (Laminariales, Phaeophyta) sporophytes in two localities with different temperature conditions

SUMMARY Sporophytes of Ecklonia cava Kjellman (Laminariales, Phaeophyta) were collected seasonally from within 3–4 replicate, 1-m2 quadrates, haphazardly placed in dense assemblages at 6–9 m depth in Tei, Tosa Bay (southern Japan; water temperature 15–29°C) from 1995 to 1996, and in Nabeta Bay, Shimoda (central Japan; water temperature 13–25°C) from 1996 to 1997. Growth rings were checked for all samples and mean values of each biometric parameter of sporophytes 1-year-old and over were compared. The plant length (stipe length + primary blade length) was always shorter in Tei sporophytes (24–52 cm) than Nabeta sporophytes (70–100 cm), the difference being mainly owing to the shorter stipe length in Tei sporophytes (7–14 cm) than in Nabeta sporophytes (54–83 cm). However, the primary blade length was sometimes longer in Tei sporophytes (12–38 cm) than in Nabeta sporophytes (14–21 cm). Stipe diameter, longest bladelet length and primary blade width were mostly less in Tei sporophytes (8.6–12.4 mm, 5.5–7.0 cm and 23.4–38.0 cm, respectively) than Nabeta sporophytes (16.4–20.2 mm, 9.2–12.0 cm and 43.0–52.6 cm, respectively). Nevertheless, the number of bladelets of sporophytes from Tei (15–28) and Nabeta (18–29) were within the same range. At Tei, 32–43% of the sporophytes had wrinkled blades in summer and autumn, whereas wrinkled primary blades or bladelets were not observed in Nabeta sporophytes throughout the experimental period. These morphometric differences of E. cava between the two localities are suggested to be dependent on environmental factors, especially seawater temperature.

Succession of sessile organisms on experimental plates immersed in Nabeta Bay, Izu Peninsula, Japan V. An integrated consideration on the definition and prediction of succession

AbstractSuccessional changes of sessile organisms over about 3 years on concrete plates immersed at depths of 1.0, 2.5, 4.0 and 5.5 m in Nabeta Bay, Shimoda, Pacific coast of Japan, were investigated from their species composition, percentage cover, and the structure, metabolism, biomass and maturity of the community for the purpose of verifying the hypothesis of succession by Margalef (1968) and Odum (1969). The process of succession was divided into five stages from a cluster analysis based on Horn's (1966) similarity in community structure. The five stages were characterized from dominant, species and 18 community attributes in terms of structure, metabolism, biomass and maturity. With the advance of stages, two large‐sized, long‐lived species, the kelp Eisenia bicyclis and the oyster Crassostrea nippona, dominated; 18 community attributes showed a directional succession ending in a constant community structure, low community metabolism, accumulation of community biomass except chlorophyll a and an enhanced degree of community maturity. This directionality in succession of community attributes was valid for the prediction of Margalef and Odum, despite a tendency for estimated daily energy budget to be more heterotrophic in such an open system. From these results, it was suggested that the definition of succession by Odum (1969) should be interpreted as the regularity in shift of dominant species, not individual species, and as the control of system by feedback mechanism developing with succession rather than community‐controlled mechanism.

Succession of sessile organisms on experimental plates immersed in Nabeta Bay, Izu Peninsula, Japan IV. Temporal changes in metabolism, biomass and maturity of community

Community succession in the metabolism, biomass and maturity of sessile organisms on concrete plates immersed at depths of 1.0, 2.5, 4.0 and 5.5 m in Nabeta Bay, Shimoda, pacific coast of Japan, was investigated over a period of about 3 yr. Gross primary production of the community (Pg) and community respiration (R) showed maxima at 10 and 13 months after immersion, and then Pg decreased significantly at all depths, whereas R was reduced only at the lower two depths. A parameter of community biomass, chlorophylla (Chl.a), showed a similar successional change to Pg. Five other parameters, i.e. dry mass (DM), ash dry mass (ADM), ash-free dry mass (AFDM), organic carbon (C) and organic nitrogen (N) increased significantly throughout succession, at least at the uppermost depth, but decreased significantly in the period 13–37 months after immersion at the lowest depth. Successional changes in five indices reflecting community maturity, i.e. the ratios of estimated daily gross primary production/estimated daily respiration (Pg/R), gross primary production/organic carbon (Pg/C), gross primary production/chlorophylla (Pg/Chl.a), organic carbon/organic nitrogen (C/N) and Margalef's pigment diversity (D430/D665), also differed among the depths, especially at 37 months after immersion. Succession at the upper two depths appeared to progress toward a mature state, as opposed to retrogression to an immature state at the lower two depths. This difference in successional changes in these 13 parameters between depths agrees with the prediction of Margalef (1968) and Odum (1969), despite the tendency for Pg/R to be more heterotrophic in an open system.

Succession of sessile organisms on experimental plates immersed in Nabeta Bay, Izu Peninsula, Japan III. Temporal changes in community structure

AbstractFrom percentage covers of sessile organisms obtained over about 3 yr by suspending concrete plates at depths of 1.0, 2.5, 4.0 and 5.5 m in Nabeta Bay, Shimoda, Pacific coast of Japan, changes of five indices of community structure, i.e. number of species (S), Shannon‐Weaver diversity (H′), evenness (J′), McNaughton's dominance (MD) and Horn's similarity (HS), were investigated throughout succession. Colonization curves became horizontal after reaching a maximum at 6 months after immersion at all depths. The number of species appeared to approach equilibrium during the first year of immersion. In the period from 13 to 37 months after immersion, the five indices indicated that communities at the upper two depths had stabilized structures within a limited range of variation, as represented by low HS values, whereas those at the lower two depths had simplified structures, as indicated by low S or H′ values. Furthermore, the results of cluster analysis of samples at four depths indicated that 13 to 37‐month communities at the upper two depths had advanced, converged structures, whereas those at the lower depths had young, non‐converged structures. The stability of community structure observed at the upper two depths could be due to domination of two long‐lived species, the kelp Eisenia bicyclis and the oyster Crassostrea nippona. On the other hand, the simplification of community structure at the lower two depths seems to be due to reduced domination of these two species as a result of disturbances such as scouring by sand.

Comparative photosynthetic studies of Ecklonia cava (Laminariales, Phaeophyta) bladelets with and without zoosporangial sori

Photosynthetic rates were compared between Ecklonia cava bladelets with and without zoosporangial sori sampled from the subtidal zone (about 5 m deep) in Nabeta Bay, Shimoda, Japan. Photosynthetic rates of bladelets were lower in the sorus portion than in the non-sorus portion on the basis of area, dry weight and chlorophyll a. Respiration rates were higher in the sorus portion than in the non-sorus portion on the basis of area and chlorophyll a, whereas they were almost the same on a dry weight basis. The differences were mainly due to a large difference in dry weight per unit bladelet area between the sorus and the non-sorus portion. Light compensation points were higher in the sorus portion than in the non-sorus portion.

Seasonal changes of photosynthetic activity of a brown algaEcklonia cava Kjellman

Samples of a brown algaEcklonia cava Kjellman from a depth of about 5 m in the subtidal zone of Nabeta Bay, Shimoda, were used to investigate photosynthesis in relation to light intensity, temperature, age and season. Photosynthesis and respiration were measured by gas-volumeters with discs (4.1 cm2) of the bladelet. The lightsaturation of photosynthesis at 20 C or atin situ temperatures occurred mostly at about 10 klux. Almost no photoinhibition of photosynthesis was observed within the light intensity range up to 30 klux. The optimum temperature for photosynthesis was around 25 C throughout a year, being slightly higher in summer and lower in winter. The light-saturated net photosynthetic rate at 20 C of the grown-up bladelets began to increase in late autumn, reached the maxima (48 μl O2 cm−2 hr−1, 16 μl O2 mg (d.w.)−1 hr−1, 2.3 μl O2 μg (chl.a)−1 hr−1) in winter, and declined to reach the minima (30 μl O2 cm−2 hr−1, 5.0 μl O2 mg(d.w.)−1 hr−1, 1.0 μl O2 μg(chl.a)−1 hr−1) in summer or early autumn. Young bladelets showed almost the same seasonal changes in the photosynthetic rates. The photosynthetic rates of the basal part were significantly lower than those of the apical part of a bladelet. The respiratory rate of the grown-up bladelet increased almost linearly with temperature in the range of 5–30 C. No marked change in the respiratory rate at 20 C was observed throughout a year.

Succession of sessile organisms on experimental plates immersed in Nabeta Bay, Izu Peninsula, Japan. II. Succession of invertebrates

Succession of sessile organisms on experimental plates immersed in Nabeta Bay, Izu Peninsula, Japan. II. Succession of invertebrates

Succession of sessile organisms on experimental plates immersed in Nabeta Bay, Izu Peninsula, Japan. I. Algal succession

Succession of sessile organisms on experimental plates immersed in Nabeta Bay, Izu Peninsula, Japan. I. Algal succession

The animal assemblage in the Ecklonia region of Nabeta Bay, Izu Peninsula, central Japan

The animal assemblage in the Ecklonia region of Nabeta Bay, Izu Peninsula, central Japan

Growth and organic production of eelgrass ( Zostera marina L.) in temperate waters of the pacific coast of Japan II. Growth analysis in winter

Growth of eelgrass ( Zostera marina L.) in winter in Nabeta Bay, Japan, was investigated in a culture experiment. The mode of vegetative growth was essentially the same as that observed in spring-summer, but specific growth rate expressed as percent increase in leaf area per day was about half the maximum observedin late April and early May. No generative organs were produced. The number of leaves on a single shoot was 4.5 ± 0.7, and the plastochrone interval, i.e. the time interval between the initiation of two successive leaves, 13 ± 3 days. Growth was apparently regulated by light. Net production by eelgrass in Nabeta Bay in January was estimated to be 1.5 g dry wt. m −2 d −1 or 0.6 g C m −2 d −1.

Growth and organic production of eelgrass ( Zostera marina L.) in temperate waters of the pacific coast of Japan. I. Growth analysis in spring–summer

The mode and dynamics of the growth of eelgrass ( Zostera marina L.) in Nabeta Bay, Japan, were investigated in a culture experiment in April–June. Two types of vegetative growth, that is, leaf elongation and new lateral shoot production, were distinguished. Formation of new leaves and defoliation were apparently synchronized, and numbers of leaves on a single vegetative shoot remained almost constant (5.5 ± 0.1). Maximum growth occurred in May. Generative (flowering) shoots were produced in May–June, and seed maturation was completed by the end of June. Mean life times of leaves on vegetative and generative shoots were 43.6 ± 1.0 and 38.7 ± 1.4 days, respectively. Net organic production by eelgrass in Nabeta Bay in June was estimated to be 7.2 g dry wt −2 day −1.