• ALGAE
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• v.20 no.4
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• pp.363-368
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• 2005

The brown alga Ascophyllum nodosum and its mutualistic, ascomycete symbiont, Mycophycias ascophylli, form a complex ‘rganism’or symbiotum. Here we show the interaction of the symbiotum to the abundant brown algal epiphyte, Elachista fucicola. Microscopy of field-collected plants shows morphological responses of A. nodosum to the common epiphyte E. fucicola. When E. fucicola attaches to A. nodosum a bundle of several to dozens of rhizoids penetrates into the host. On the surface of the host, the cells proliferate to form a donut-shaped ring, 100-200 μm in height that surrounds the thallus of E. fucicola. A pit forms in advance of the rhizoids and the cells of A. nodosum break down. This leaves the network of fungal hyphae partially intact and intermingling with the epiphyte rhizoids and its lowermost cells. After the pit is formed, the cells of A. nodosum bordering the infection chamber redifferentiate an epidermal layer. Neither the host nor its mutualistic fungus, M. ascophylli appears to recognize E. fucicola as an invader and to prevent the attachment and growth of this epiphyte. Based on the physical damage to the host caused by invading rhizoids, we conclude that the relationship of E. fucicola to A. nodosum is that of a parasite and its host.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.10
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• pp.1514-1518
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• 2006

English crossbred steers (n = 32) and heifers (n = 32) were fed a corn-based finishing diet and supplemented with 2% Ascophyllum nodosum on a DM basis to for various feeding stages of the 119 d feeding period determine the supplementation strategy that maximized intramuscular fat deposition as determined by quality grade. All cattle were implanted with Ralgro$^{(R)}$ on d 36 of the trial and re-implanted with Revalor-S$^{(R)}$ or Revalor-H$^{(R)}$ on d 92. Cattle were blocked by sex and divided into one control and three treatment groups receiving Ascophyllum nodosum. Treatment 1 (trt 1) received Ascophyllum nodosum from d 36 to 50 of the feeding period, trt 2 received Ascophyllum nodosum for the last 14 d of the feeding period, and trt 3 which received Ascophyllum nodosum for both d 36-50 and the last 14 d of the feeding period. Cattle were weighted initially ($385{\pm}4.53kg$) and every 28 d following until they reach an average BW of $554{\pm}7.46kg$. No effect for Ascophyllum nodosum supplementation was found on measured performance characteristics. All treatment groups supplemented with Ascophyllum nodosum had higher actual marbling scores (p<0.05) than controls. Trt 1 was found to have a highest marbling score (572.5; p<0.05), whereas the control group having the lowest marbling score (473.8). Trt 1 had a higher quality grade (5.25; p<0.05) than the control (3.94) group, but did not differ from trt 2 (4.56; p = 0.105) and trt 3 (4.75; p = 0.236) where high Select = 4, and low Choice = 5. Trt 2 did not differ from trt 3 (p = 0.655), or the control group (p = 0.140) for quality grade. However, trt 3 did tend to differ (p = 0.057) from the control group for quality grade. Control group animals graded 25% Choice, 62.5% Select; trt 1 graded 75% Choice, 18.8% Select; trt 2 graded 62.5% Choice, 25% Select and trt 3 graded 56.3% Choice and 31.2% Select. Overall, treatment groups had a 39.6% increase in Choice quality grade and a 37.5% decrease in Select quality grade when compared to the control animals.

• ALGAE
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• v.26 no.3
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• pp.253-263
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• 2011

Phenotypic plasticity was examined in the economically and ecologically important brown alga Ascophyllum nodosum in southwestern Nova Scotia, considering specifically how nutrient loading affected its vegetative and reproductive features. To determine this, we examined morphometric changes in A. nodosum from two sites receiving direct effluent impacts from a land-based finfish aquaculture facility and from two control sites, approximately 2 km away from the aquaculture facility in opposite directions. Fronds from test sites were significantly younger than from control sites (5 y vs. 8 y); however, fronds from farm sites were significantly larger (219 g vs. 90 g) because of their higher growth rates. Thalli from farm sites had greater reproductive potential, as shown by numbers of receptacle initials (797 initials vs. 281 initials). These results suggest limited nutrient inflows from land-based aquaculture may positively affect adjacent Ascophyllum populations by inducing higher growth rates. We conclude that the coordination of effluent management from land-based aquaculture with natural resource harvesting of A. nodosum may be beneficial. Further study is necessary to determine the limits of nutrient loading for this potentially beneficial outcome.

• ALGAE
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• v.29 no.4
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• pp.321-331
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• 2014

Vertebrata lanosa is an abundant and obligate red algal epiphyte of Ascophyllum nodosum that forms part of a complex and highly integrated symbiotic system that includes the ascomycete, Mycophycias ascophylli. As part of ongoing studies to resolve interactions among species in the symbiosis, we used pulse amplitude modulation fluorimetry of chlorophyll a fluorescence, from photosystem II (PSII), to measure the maximum quantum yield ($F_v/F_m$) of PSII [$QY(II)_{max}$] and relative photosynthetic electron transport rates (rETR), as a function of light intensity, in order to evaluate the photosynthetic capacity of the two algal symbionts in the field and in the laboratory under different treatments. Our primary question was 'Is the ecological integration of these species reflected in a corresponding physiological integration involving photosynthetic process?' In the laboratory we measured changes in $QY(II)_{max}$ in thalli of V. lanosa and A. nodosum over one week periods when maintained together in either attached or detached treatments or when maintained separated from each other. While the $QY(II)_{max}$ of PSII of A. nodosum remained high and showed no significant variation among treatments, V. lanosa showed decreasing performance in the following conditions: V. lanosa attached to A. nodosum, V. lanosa in the same culture, but not attached to A. nodosum, and V. lanosa alone. These results are consistent with observations in which rETR was reduced in V. lanosa maintained alone versus attached to A. nodosum. Values for $QY(II)_{max}$ in V. lanosa measured in the field in fully submerged thalli were similar to those measured in the laboratory when V. lanosa was attached to it obligate host A. nodosum. Our results provide evidence of a physiological association of the epiphyte and its host that reflects the known ecology.

• Korean Journal of Environment and Ecology
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• v.29 no.1
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• pp.7-13
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• 2015

To examine the relationship between competition and environmental factors, the germlings of Ascophyllum nodosum (L) Le Jolis and Fucus vesiculosus L. were cultured in monocultures and mixtures of the two species under two different exposure and nutrient levels. Both intra- and inter-specific competition were examined in comparison of the mortality and growth of germlings in monocultures and mixtures of the two species. The mortality of germlings increased with increasing density and emergence periods both in the monoculture and mixtures of the two species, and the mortality of Ascophyllum was significantly higher than that of Fucus both in submerged and emerged treatments. The growth of germlings of both species reduced with increasing density but F. vesiculosus always grew faster than Ascophyllum. The values of log output ratio were more than 0.1, indicating that Fucus 'won' in the competitive battles with Ascophyllum under two nutrient- and air-exposure levels. Log output ratio was greater in high than in low nutrients, indicating that the growth of Fucus is more enhanced than that of Ascophyllum in high nutrients. In the present study, the outcome of inter specific competition between germlings of Fucus vesiculosus and Ascophyllum nodosum was slightly altered by duration of emergence and nutrient concentration, but not to such an extent as to change the outcome.

• ALGAE
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• v.22 no.2
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• pp.107-116
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• 2007

Annual growth segments of Ascophyllum nodosum (L.) Le Jolis (Fucales, Fucaceae) are denoted by air bladders that form each spring. By examining annual growth segments, it may be possible to infer information about the physical conditions during the growth period; however, it is uncertain whether the annual segments will expand in size after the initial growth. We examined A. nodosum segments from three populations in Nova Scotia, and statistically evaluated whether the annual growth (length, mass, and maximum diameter) of segments was independent of the age of the frond, whether the segments increased in size after the initial growth, and whether the segment lengths were correlated with mean water temperatures and mean air temperatures when the segments were formed. We found that the growth in length of A. nodosum is dependent on the age of the frond, but frond age explained less than 12 % of the overall variation in length. However, the mass and maximum diameter of segments were independent of the age of the frond. Differences occurred between the lengths of segments formed in different years, but there was no significant correlation with regional mean water or air temperatures. This study indicates that the length of A. nodosum segments may be an indicator of the annual physical characteristics of a site, but future studies are needed to identify which factors have the strongest influence on growth patterns.

• ALGAE
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• v.20 no.4
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• pp.353-361
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• 2005

Ascophyllum nodosum (L.) Le Jolis has a systemic infection with the ascomycete Mycophycias ascophylli (Cotton) Kohlmeyer and Volkmann-Kohlmeyer with which it establishese a mutualistic symbiosis. In addition, A. nodosum is the host for the obligate red algal epiphyte, Vertebrata lanosa (L.) Christensen. Using light and electron microscopy we describe morphological and cytochemical changes occurring as a consequence of rhizoid penetration of V. lanosa into cortical host tissue. Rhizoids induce localized cell necrosis based on physical damage during rhizoid penetration. Host cells adjacent to the rhizoid selectively undergo a hypersensitive reaction in which they become darkly pigmented and become foci for hyphal development. Light and electron microscopy show that M. ascophylli forms dense hyphal aggregations on the surface of the V. lanosa rhizoid and extensive endophytic hyphal growths in the rhizoid wall. This is the first morphological evidence of an interaction between M. ascophylli and V. lanosa. We speculate that M. ascophylli may be interacting with V. lanosa to limit tissue damage to their shared host. In addition, the fungus provides a potential pathway for the transfer of materials (e.g., nutrients and photosynthate) between the two phototrophs.

• ALGAE
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• v.20 no.3
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• pp.225-232
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• 2005

Optical microscopy of recently living and cleared material of the fucoid, Ascophyllum nodosum (L.) Le Jolis, revealed novel aspects of its interaction with the ascomycete Mycophycias ascophylli (Cotton) Kohlmeyer and Kohlmeyer (previously Mycosphaerella ascophylli Cotton). Most host cells are associated with hyphae by lateral attachment of cell walls. Hyphae form extensive networks throughout the host thallus and show considerable differentiation in the various host tissues. In the base of epidermal cells, hyphae form multicellular rings around each host cell to produce a continuous network. In medullary regions, long, relatively unbranched and longitudinally aligned hyphae occur, with radial branches extending into cortical regions. Scattered in the inner cortex of host tissue are numerous multicellular nodes of smaller, polygonal to irregular shaped cells with five or more radiating arms of hyphae. Individual hyphal cells show a variety of specializations including swellings and appressoria-like attachments to some host cells. These observations provide the morphological basis for the mutualistic symbiosis supported by recent experimental work. We conclude that this association is best described by the term “symbiotum.”

• ALGAE
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• v.24 no.2
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• pp.93-104
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• 2009

Imaging-PAM fluorometry was used to assess the chlorophyll a fluorescence parameter ${\Phi}_{PSII}$ (effective quantum yield) in Frcus vesiculosus. F. disttchus. ssp. distichus and AscophyIIum nodosum. The objective was to show variadon in fluorescence yield associated with age and frond organ, and to illustrate the spatial scales at which photosynthetic parameters vary on fucoid thalli. In addition, our species represented taxa in different but related genera, species with different ecoloeies (rock pool and non rock pool species), morphologies (with and without air bladders) and longevities (several to 20 or more years). A further objective was to determine the extent to which photosynthetic parameters reflected these differences- Effective quantum yield declined substantially with age in F. vesiculosus and F. distichus ssp. distichus, whereas ${\Phi}_{PSII}$ in A. nodosum was maximal after three years. In A. nodosum ${\Phi}_{PSII}$ was still high in branch segments at least seven years old. Older branches of A. nodosum showed relatively higher and more homogeneous photosynthetic capacity relative to Fucus species. Surfaces of air bladders in A. nodosum and F. vesicu- losus had ${\Phi}_{PSII}$ that was not significantly different from the highest rates, achieved in these species. The heterogene- ity of photosynthetic efficiency is consistent with morphological and developmental differences among the species and their ecology. in particular the longevity of A. nodosum fronds.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.275-280
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• 2004

In this study, the effcts of kelp (Ascophyllum nodosum) meal on growth and immune responses of parrot fish (Oplegnathus fasciatus) were studied. Fish were fed an experimental diet supplemented with $2{\%}\;and\;5{\%}$ kelp meal in a controled diet. Several factors such as weight gain, hematological parameters and nonspecific immune responses were evaluated far 0, 2, 4 and 8 weeks after the administration of the kelp meal supplemented diet. Weight gain in the fish fed the diet supplemented with $2{\%}\;and\;5{\%}$ kelp meal was not significant among the tested groups. The NBT reaction of the phagocytes in the head kidney and the phagocytic rate/index of phagocytes in the peripheral blood were significantly higher than the control group. But, there was no significant difference both in complement bactericidal activity, mucus Iysozyme activity and hematology among each group.