Nursery Culture Research Articles

A partial substitution of microalgae with single cell detritus produced from seaweed (Porphyra haitanensis) for the nursery culture of tropical oyster (Crassostrea belcheri)

Oyster seed production in hatchery and nursery systems has relied on the production of microalgae, which is cost effective, but often unpredictable. The development of a satisfactory substitute diet would greatly reduce production costs of hatchery operations. Single cell detritus (SCD) production from seaweed (Porphyra haitanensis) may have great potential as a partial substitute for microalgae. In this experiment, a technique for producing SCD was developed and the product was used as a partial substitute for microalgae for the nursery culture of juvenile tropical oysters (Crassostrea belcheri) in a hatchery setting. A reverse osmosis technique was used on ground seaweed (particle size <200 μm) immersed in freshwater and placed on a shaker at 100 rpm for 2 h before being returned to seawater. This technique was shown to be highly effective for SCD production with a density of 33.7 ± 7.0 × 104 cell mL−1 and the percentage of SCD particle diameter <20 μm was 89.2%. A partial replacement of microalgae with SCD was found to be unsuitable for nursing oyster larvae. For juvenile oysters (shell width 1.85 ± 0.03 mm and shell length 1.78 ± 0.06 mm) substituting 75% of microalgae with SCD showed lower absolute shell growth, and lower daily yields and survival rates when compared to rates substituting 50% or lower substitution with SCD, or 100% microalgae (P < 0.05). It was found that substituting 50% of the traditional microalgae with SCD produced from seaweed (P. haitanensis) can be used as a partial microalgae substitute for the nursery culture of the juvenile tropical oyster.

Efectos de la posición en el arrecife y del linaje en el crecimiento de Acropora cervicornis (Scleractinia:Acroporidae) en una plantación de vivero en Bahía Montego, Jamaica

The reef-building coral Acropora cervicornis was a dominant ecosystem element on the Caribbean reef until the 1980s, when it declined by some 97% due primarily to anthropogenic ecosystem changes and disease. This branching species expanded its colony footprint and achieved local dominance largely through fragmentation and regrowth, thus is suited to nursery culture towards restoration. In this experiment, fragments of Acropora cervicornis of four lineages or genets were followed and measured for growth and health over 12 months in 2006 and 2007 on buoyant drop-loop line nurseries at one shallow and one deep fore-reef site in Montego Bay, Jamaica. Sixty-five of these corals were then out-planted to wild reef sites of similar depth and condition to their respective nurseries and monitored photographically for 11 months through 2007 and 2008. A period of rapid death was seen in the out-planted material at both sites over the first four months, followed by a period of relative stability or recuperation. Hermodice carunculata predation was the primary problem in the shallow fore-reef, and was combined with a banding syndrome at the deeper site. This syndrome was noted in the samples prior to planting, during a one week storage period on the seafloor. Continued slow decline occurred in the subsequent seven months in the shallow fore-reef site; however, regrowth was noted in the deeper site in the remaining material. Including these losses, final total live coral length was more than fourfold greater than the initial wild harvest: a net increase through multi-stage propagative restoration or coral gardening. Returns were noted particularly in the faster-growing genets of the nursery and larger planted corals tended to retain more material at eleven months, suggesting that propagative restoration programmes invest in stronger genets and larger corals. Adaptive management and maintenance gardening of the planted material and reef would likely have greatly improved outcomes. Rev. Biol. Trop. 62 (Suppl. 3): 95-106. Epub 2014 September 01.

Comparative efficiency and yield in different systems and densities at the nursery culture phase of the oyster Crassostrea gigas in southern Brazil

This study was conducted to compare different aquaculture systems and seed densities for the nursery phase ofCrassostrea gigas in Brazil. Small oyster seeds (2 mm in height) reared in three nursery systems (same area/floor), a lantern net, a bouncing bucket or a floating box were compared with three initial stocking densities (50, 100 and 200 mL of seeds/system floor). As density increased, there was a significant decline in seed growth and yield, mainly in the lantern nets (P=0.0002). Better yields were observed in the box (P=0.005) and bucket systems (P=0.02) under densities of 50 and 100 mL. However, at the highest density, the nursery box system had the highest seed yield when compared to the lantern net and bucket systems (P=0.003). The results showed that the floating box was the most efficient system tested with a survival of 54% at a density of 100 mL. This was more than twice the survival for the same volumes used in the nursery lantern nets (24%), which was the most common culture method in Brazil prior to this experiment (2002). An additional advantage is the reduced cost of starting with 2.0 mm seeds that cost 50% less than the usual 4.0 to 8.0 mm seeds. These results showed the efficiency of the floating box system, which is currently used by over 90% of oyster producers in Brazil.

Container volume and growing density influence western larch (Larix occidentalis Nutt.) seedling development during nursery culture and establishment

Larch tree species (Larix Mill.) are both ecologically and commercially valuable in their native range and are the focus of many restoration, afforestation, and commercial reforestation efforts in the boreal forests of the northern hemisphere. Land use change, shifting climate, and poor natural regeneration are making it increasingly difficult to establish the species; therefore, artificial regeneration is critical to ensure this timber species maintains its productive role on the landscape. New stocktypes are continually being developed to aid target seedlings for difficult sites, and critical, non-confounding evaluations of them are needed for target seedling development. This research evaluates the effect of container parameters on potential target seedlings. It examines tolerance thresholds of western larch (Larix occidentalis Nutt.) with respect to moisture and temperature status in the rhizosphere during early establishment. A suite of morphological measurements was used to assess seedling quality and relative performance following transplant. Modifying a commercially available container developed four distinct stocktypes of 111, 143, 175 and 207 ml that were paired with a volume-dependent nutrient regime at two culturing densities. Seedling phenotype was affected to a greater extent by container density than by container volume. Despite changes to container volume, root:shoot were found to be similar, indicating benefits of a tailored nutrient regime during nursery culture. Simulated field trials revealed that a low density growing arrangement improved post-transplant seedling growth, specifically root growth. Also, the 207 ml container facilitated greater growth in dry soil conditions compared to smaller containers. Lower (10 °C) rhizosphere temperature hindered root growth; however, seedling survival was 100 %, warranting the testing of earlier outplanting windows for this species. This evaluation of stocktype performance contributes to a greater body of work with this species and its congeners, which will ultimately benefit reforestation and afforestation efforts alike.

Effects of grazing by herbivorous gastropod (Trochus niloticus) on the survivorship of cultured coral spat

The technology in the production of sexual coral propagules for coral reef restoration is being actively developed recently to address concerns on the low genetic diversity in coral populations restored through transplantation of coral materials derived from fragmentation. In this study, we produced coral spat attached to rubble and determined the effect of the addition of hatchery-reared trochus, a herbivorous gastropod, at two densities (one and two trochus per cage, equivalent to four and eight trochus per square meter, respectively) on the survivorship of the spat cultured in cages at the hatchery and in situ nursery. After 5 weeks of culture in the hatchery, spat survivorship was significantly higher in the two per cage trochus treatment (18.3% ± 6.7%, mean ± sd) than in the control (5.5% ± 1.7%), with the one per cage trochus treatment having intermediate spat survival (12.6% ± 7.9%). The enhanced spat survivorship, though not apparent in the in situ nursery culture, is attributed to the grazing effect of trochus as significantly lower turf algal cover was observed in rubble placed in two per cage trochus treatment (44.8% ± 3.2%) than in the one per cage trochus treatment and control (80.2% ± 6.5% and 76.3% ± 5.0%, respectively). This study demonstrates that trochus can be used to control algal cover and enhance survivorship of coral spat in caged culture, at least in the hatchery, for the production of sexually derived transplant materials for coral reef restoration.

High-density nursery culture of recently-settled blue king crabs (Paralithodes platypus): Comparisons to red king crabs (Paralithodes camtschaticus)

Stock enhancement through the release of cultured juveniles has been suggested as a possible recovery tool for depleted red (Paralithodes camtschaticus) and blue (Paralithodes platypus) king crab populations in Alaska, USA. Considerable progress has been made in the past decade in red king crab culture technology, but similar technologies are less developed for blue king crabs. As part of a stock enhancement feasibility study, hatchery-raised blue king crab juveniles were cultured from larvae of ovigerous females collected off Saint Matthew Island, Alaska. Juvenile instars were then cultured in indoor nursery containers for 42days at stocking densities of 500, 1000, 2000, 4000, and 6000crabsm−2 starting at metamorphosis to the first instar stage (C1). At day 42, survival was above 90% at all the densities, but had a slightly decreasing trend that ranged from 96% at 500crabsm−2 to 90% at 6000crabsm−2. The numbers of crabs cannibalized increased with density, but the overall increase in crab biomass offset the negative effects of cannibalism. Survival rates and biomass production for the first 42days post-settlement is much higher for blue king crabs compared to red king crabs reared under identical conditions. The low rate of cannibalism implies that blue king crabs are well suited for large-scale hatchery culture. Our results suggest that these two closely related crab species can be reared at different stocking densities immediately flowing settlement and that high densities will maximize hatchery efficiency for blue king crabs. Future studies should investigate longer term nursery culture, beyond 42days, to refine protocols for extended blue king crab rearing. Improving nursery techniques will boost the productivity and financial viability of a large-scale stock enhancement program.

Exponential nutrient loading shortens the cultural period of Larix olgensis seedlings

Traditional nursery culture of Changbai larch (Larix olgensis Henry) in Northeast China requires up to a 2-year nursery production period. The high cost of seedling culture for this duration has been identified as a constraint. As a potential means to help to shorten the cultural period, we evaluated growth, biomass accumulation, and nitrogen (N) uptake dynamics of 1-year-old seedlings subjected to nutrient-loading treatments at intensive rates of 500 mg N seedling−1 supplied exponentially (E500) and 135 mg N seedling−1 supplied exponentially (E135) or conventionally (constant). Also included were an unfertilized control and the standard fertilizer regime for 2-year-old seedling production (77 mg N seedling−1 supplied conventionally over 2 years). At the end of nursery culture, though seedlings in the constant treatment had more biomass and N accumulation at the whole-seedling level, much of this was allocated to needles. While seedlings in the E500 treatment exhibited signs of toxicity, those in the E135 treatment had equivalent end-of-nursery N concentration in woody tissues to those produced over 2 years; root collar increment and survival 69 d after outplanting were also similar. Our results suggest that exponential nutrient loading at an optimal rate could increase available nutrient reserves in woody tissues of deciduous tree seedlings, therefore having the potential to improve seedling performance after outplanting.

Effect of age and planting site on survival and growth of seedlings of Juniperus thurifera L.

L’objectif de cette étude était de comparer la survie et la croissance des plants de Juniperus thurifera d’une saison de croissance cultivés dans des conteneurs de deux capacités (200 ml et 300 ml) à des plants de deux saisons de croissance cultivés dans une seule taille de conteneur (300 ml). Les plants ont été cultivés en 2006 et 2007 à partir du même lot de semences et suivant le même schéma annuel de fertilisation. Ainsi une dose de 135,05 mg de N a été appliquée pour les plants d’un an et une dose de 271 mg de N pour les plants de deux ans. Les plants ont été transplantés en février 2008 dans deux sites localisés à Monreal del Campo (Teruel) et Buenhache de la Sierra (Cuenca) pour étudier leur survie et leur développement. La survie au cours de la première année était de 100 % dans tous les traitements à Monreal del Campo, tandis qu’à Buenhache la mortalité des plants d’un an cultivés dans des conteneurs de 300 ml a été significativement plus élevée que dans les deux autres traitements. Le choix du site de plantation et du type de culture des plants influence donc la réussite du reboisement.

Where to Settle—Settlement Preferences of Mytilus galloprovincialis and Choice of Habitat at a Micro Spatial Scale

The global mussel aquaculture industry uses specialised spat catching and nursery culture ropes made of multi-filament synthetic and natural fibres to optimise settlement and retention of mussels for on-growing. However, the settlement ecology and preferences of mussels are poorly understood and only sparse information exists in a commercial context. This study quantified the settlement preferences of pediveligers and plantigrades of Mytilus galloprovincialis on increasingly complex surfaces and settlement locations at a micro spatial scale on and within ropes under commercial hatchery operating conditions using optical microscopy and X-ray micro-computed tomography (µCT). M. galloprovincialis has clear settlement preferences for more complex materials and high selectivity for settlement sites from the pediveliger through to the plantigrade stage. Pediveligers of M. galloprovincialis initially settle inside specialised culture ropes. Larger pediveligers were located close to the exterior of ropes as they increased in size over time. In contrast, smaller individuals were located deeper inside of the ropes over time. This study demonstrates that X-ray µCT is an excellent non-destructive technique for mapping settlement and attachment sites of individuals as early as one day post settlement, and quantifies the number and location of settled individuals on and within ropes as a tool to understand and optimise settlement in complex multi-dimensional materials and environments.

Root growth of containerized lodgepole pine seedlings in response to Ascophyllum nodosum extract application during nursery culture

MacDonald, J. E., Hacking, J., Weng, Y. and Norrie, J. 2012. Root growth of containerized lodgepole pine seedlings in response to Ascophyllum nodosum extract application during nursery culture. Can. J. Plant Sci. 92: 1207-1212. Vigorous root growth immediately after spring planting is crucial to ensure a well-developed root system before the occurrence of drought events associated with climate change. The objective of this study was to enhance spring root growth of containerized lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings. Seedling culture began in April. In September, seedlings were root drenched with an extract of the brown marine alga Ascophyllum nodosum (L.) Le Jolis in finisher fertilizer at rates of 1:750, 1:500, and 1:250. Finisher fertilizer alone served as control. Applications were made three or six times. Seedling culture continued until lifting in December, and then seedlings were freezer stored. Frequency of application had no effect on root growth, whereas rate of...

Root growth of containerized lodgepole pine seedlings in response to Ascophyllum nodosum extract application during nursery culture

MacDonald, J. E., Hacking, J., Weng, Y. and Norrie, J. 2012. Root growth of containerized lodgepole pine seedlings in response to Ascophyllum nodosum extract application during nursery culture. Can. J. Plant Sci. 92: 1207–1212. Vigorous root growth immediately after spring planting is crucial to ensure a well-developed root system before the occurrence of drought events associated with climate change. The objective of this study was to enhance spring root growth of containerized lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings. Seedling culture began in April. In September, seedlings were root drenched with an extract of the brown marine alga Ascophyllum nodosum (L.) Le Jolis in finisher fertilizer at rates of 1:750, 1:500, and 1:250. Finisher fertilizer alone served as control. Applications were made three or six times. Seedling culture continued until lifting in December, and then seedlings were freezer stored. Frequency of application had no effect on root growth, whereas rate of application had a significant effect. Compared with control, the 1:750, 1:500, and 1:250 rates significantly reduced total length of the root system in mid October. After overwintering and growing under favorable environmental conditions for 21 d, the 1:500 rate significantly increased the total number of white roots, as well as the number of both short and long white roots. These results suggest that application of Ascophyllum nodosum extract may be a valuable nursery practice to increase spring root growth, thereby enhancing drought resistance.

Artificial seed production and cultivation of the edible brown alga Sargassum naozhouense Tseng et Lu

Sargassum naozhouense Tseng et Lu is a perennial brown alga found in the coastal area of Leizhou Peninsula, Guangdong, China, and it has considerable commercial potential for further exploitation. To develop a commercial-scale aquaculture of this edible species, the growth, maturation, artificial seeding, and cultivation of this alga and harmful co-existing organisms were investigated from March 2009 to April 2010. In the alga’s natural environment, the receptacles began to form in April and bloomed in May. Artificial cultivation reduced the time required for thalli maturation by at least 1 month. Seedlings were cultured for 1 month in tanks with flowing seawater, until the seedlings had grown to a length of 1.5–2.0 mm. The seedlings were then transferred to a nursery culture ground at sea for an additional 5 months until they reached a mean length of 5 cm. The control of fouling organisms was crucial for establishing a successful seedling culture both indoors and at sea. Afterwards, 45,000 germlings were reared in a grow-out sea area using a full floating raft cultivation system on 2-km-long ropes. The mean yield from this rearing was 1,750 kg wet wt. km−1 culture rope during the farming period of 95 days. Adult S. naozhouense has a greater tolerance to high temperatures than other cultivated Sargassum species and can withstand a temperature as high as 33.7 °C. A preliminary commercial cultivation protocol was also established. The results demonstrate the potential to aquaculture S. naozhouense at relatively high seawater temperatures.

Nursery Culture of Grouper (Epinephelus fuscoguttatus Forsskal) and Sea Bass (Lates calcarifer Bloch) in Brackish Water Ponds: Co-Feeding of Zooplankton and Formulated Diets Containing L-Tryptophan

This study compared co-feeding zooplankton (ZP, mixed copepods and mysids) and formulated diets (FD) supplemented with L-tryptophan (TRP) on the survival and growth of grouper and sea bass fry nursed in brackish water ponds. Grouper (84 fry m−3) and sea bass (150 fry m−3) were reared for 30 days and 60 days, respectively, in net cages within two separate 743 m2 nursery ponds. Five treatments (with three replicates each) were compared (P < 0.05): FD-1 = ZP + basal FD (no added TRP, but containing 0.29% endogenous TRP); FD-2 = ZP + (FD 0.58% TRP); FD-3 = ZP + (FD 1.22% TRP); FD-4 = ZP + (FD 2.50% TRP); and FD-5 = minced fish (Sardinella sp.) + basal FD (no additional TRP). TRP supplementation in grouper diets produced no significant affect on growth but increased survival at rates of 0.58% and above. TRP supplementation at 2.5% (FD-4) produced significantly better sea bass growth than other diets but had no affect on survival. Zooplankton improved both survival and growth in both grouper and sea bass juveniles compared to the minced fish diet, and may be a practical and lower cost alternative to indoor nursing.

Partitioning of carbon allocation to reserves or growth determines future performance of aspen seedlings

Increasingly, trembling aspen (Populus tremuloides Michx.) is being planted in stressful situations such as forest land reclamation, afforestation and forest restoration in North America. This is due to its fast potential for growth and high resiliency, but its indeterminate growth strategy provides a special challenge in creating suitable planting stock for these sites. Clues from naturally established aspen seedlings suggest that root total non-structural carbohydrate (TNC) reserves and root:shoot ratio could be strongly related to subsequent seedling establishment and growth. Carbon allocation in plants is generally partitioned between reserve accumulation and growth and development. Under conditions in controlled nurseries, the allocation of carbohydrates to reserves could be manipulated in order to produce seedlings designed for specific environmental conditions. To manipulate seedling characteristics we attempted to induce premature bud set during nursery culture while allowing continued photosynthesis. Treatments included applying different fertilizer regimes, light intensities, reducing photoperiod and use of a shoot growth inhibitor. The shoot growth inhibitor was the most reliable treatment and resulted in complete bud set, while blackout was successful only when seedlings were grown outside. Low nutrient treatments also resulted in early bud set; however, leaves were abscised much earlier. There was a distinct trade-off between growth and reserve accumulation with the late bud set. A longer period of height growth reduced root and total TNC reserves, while early bud set allowed for continued photosynthesis and produced the highest levels of root and total TNC reserves in seedlings. Increased TNC reserves of aspen planting stock was positively related to height growth after outplanting, with root TNC reserves as high as 33% of dry weight and root:shoot ratios greater than 2 associated with the best growth.

Effect of Color and Mesh Size on Growth Performance and Net Fouling of Suspended Hatchery Trays for Crassostrea belcheri (Sowerby 1871) Oysters

The effects of mesh size and color on growth performance and net fouling of suspended plastic mesh trays during nursery culture of spat and juvenile hatchery-reared tropical oysters, Crassostrea belcheri (Sowerby 1871), was studied for 60 days. Mesh diameter significantly affected the absolute growth rate in shell width, the specific growth rate, and the final survival of smallspat (p&lt;0.05). Mesh diameter and color had non-significant effects (p&gt;0.05) on the growth performance of large spat. There were no significant interactive effects between mesh size and color on growth performance of small or large spats. Mesh size and color significantly affected (p&lt;0.05) the net fouling rate: the rate was high on small mesh (0.35 cm) and low on large mesh (0.72 cm) for small spat, high on black trays and low on green trays for large spat. There were no significant interactive effects of mesh size and color (p&gt;0.05) on the fouling rate for either small or large spats.

Two provenances of Quercus ilex ssp. ballota (Desf) Samp. nursery seedlings have different response to frost tolerance and autumn fertilization

Despite evidences that Holm oak has a high plasticity and great adaptability, there is limited or contradictory knowledge of the morphological and physiological variability of this species. Holm oak has been widely used for reforestation projects in Mediterranean areas, but has frequently shown poor field performance. We hypothesized that Holm oak has inter-population differences in physiological responses to abiotic stressors that could affect reforestation success. The influence of nursery culture on the characteristics of Holm oaks from different provenances has not been explored in depth. Thus, we studied the effect of nursery autumn fertilization on morphological traits, frost tolerance, root growth potential, and nutritional status of two Spanish provenances of Holm oak, La Alcarria (a region with inland Mediterranean climate) and Sierra Morena Occidental (a region with a warm coastal Mediterranean climate). There were significant differences between the provenances in frost tolerance, biomass allocation, and leaf nutrient content, suggesting a role of genetic factors. The leaves of seedlings from La Alcarria had less visual damage at −12°C than seedlings from the warmer provenance (45% vs. 92%). Seedlings from La Alcarria, compared to those from Sierra Morena, had higher leaf P concentration (0.17% vs. 0.15%), greater stem diameter (3.1 mm vs. 2.7 mm), lower shoot-to-root dry mass ratio (0.46 vs. 0.53), and lower slenderness (4.03 vs. 5.31). For both provenances, N autumn fertilization improved growth, root growth potential, cold hardiness, and nutritional status of seedlings. We suggest that forest reforestation programs should consider to a greater extent Holm oak provenances and their tolerances to different abiotic stressors.

Growth, Gas Exchange, Foliar Nitrogen Content, and Water Use of Subirrigated and Overhead-irrigated Populus tremuloides Michx. Seedlings

Because limitations on water used by container nurseries has become commonplace, nursery growers will have to improve irrigation management. Subirrigation systems may provide an alternative to overhead irrigation systems by mitigating groundwater pollution and excessive water consumption. Seedling growth, gas exchange, leaf nitrogen (N) content, and water use were compared between overhead irrigation and subirrigation systems used to produce trembling aspen (Populus tremuloides Michx.) seedlings. After 3 months of nursery culture, subirrigation resulted in a 45% reduction in water use compared with overhead irrigation. At the end of the growing season, subirrigated seedlings had lower net photosynthetic assimilation, stomatal conductance (gS), and leaf area, indicating earlier leaf senescence. However, no significant differences were detected for biomass, leaf N content, height, root-collar diameter, or root volume. Thus, we suggest that subirrigation systems offer promising potential for aspen seedling production when compared with overhead irrigation given the added benefits of water conservation and reduced nutrient runoff. Continuing emphasis on refinement such as determining the plant water requirements based on growth and development as well as container configuration is needed so that the intended benefits of using subirrigation can be realized.

Assessing alternative grazing-tolerant algae for nursery culture of abalone, Haliotis iris

Feeding during the nursery stage of abalone aquaculture, from larval settlement to 10 mm in shell length (SL), is a major challenge in the intensification of abalone aquaculture. Commercial abalone nurseries typically settle larvae onto vertical plastic plates coated with algae that act as a settlement cue and an important post-settlement food source. It becomes increasingly difficult to maintain an adequate algal food supply as the abalones grow and for this purpose many nurseries use the alga, Ulvella lens, as it is a very effective settlement cue as well as offering a resilient food source for the developing abalones. However, juvenile abalones can deplete a film of diatoms on the plates before they are capable of ingesting U. lens, and once abalone reach ~ 5 mm SL the high grazing pressure may exceed even what U. lens can support, requiring nurseries to provide additional cultured algae or prematurely wean the juveniles onto manufactured diets. Three prospective microfilamentous algal species isolated from the tanks of a commercial abalone facility, were selected as potentially suitable nursery algae as they demonstrated resistance to intensive juvenile grazing pressure, displayed rapid vegetative growth, and could be triggered to mass sporulate as a means of rapidly coating nursery tanks. The current study involved two experiments and assessed the suitability of each species as a live algal feed for juvenile abalones compared to U. lens. These experiments measured: (1) ingestibility and grazing resistance of each alga against juvenile abalone 1–8 mm SL, and (2) the ability of each species to recover once grazers had been removed. Two algae (Ulvophyceae sp. 1 and 3) demonstrated the desirable properties of being easily grazed by abalones of a smaller size (average SL 2.33 mm and 2.20 mm respectively) than U. lens (2.89 mm) yet provide an algal film that is likely to be resilient and durable under grazing pressure. These algae also displayed significantly greater rates of recovery following grazing than U. lens (p < 0.01), an important attribute for restoring algal films in nursery systems between grazing events or between batches of juvenile abalones. The results of this study indicate that these novel algae have a combination of desirable characteristics for use in commercial abalone nurseries. Further experiments in commercial scale nursery systems should be pursued to assess the food value and performance of these species as a feed for juvenile abalones.

Minimizing nutrient leaching and improving nutrient use efficiency of Liriodendron tulipifera and Larix leptolepis in a container nursery system

Fertilization is essential to seedling production in nursery culture, but excessive fertilization can contaminate surface and ground water around the nursery. The optimal fertilization practice is that which maximizes seedling growth and minimizes nutrient loss. We tested three fertilization strategies: (1) constant fertilization (2) a three-stage rate, and (3) exponential fertilization on Liriodendron tulipifera and Larix leptolepis containerized seedlings. Growth performance, nutrient uptake, and nutrient loss in leaching were measured. Height, root collar diameter, and dry weight of both species were not significantly different among treatments even though the nutrient supply of the exponential treatment was half that of the constant and three-stage treatments. Generally, nutrient losses in leached solutions were higher in constant and three-stage than the exponential treatment. Nutrient use efficiency was calculated as the ratio of the nutrient content of the seedlings to the amount of nutrient applied to the containers. The nitrogen use efficiency in the constant, three-stage, and exponential treatments was 63, 61, and 85% for yellow poplar, respectively, and 35, 30, and 53% for larch. Similar results were obtained for phosphorus and potassium. Thus, the exponential treatment had the highest nutrient use efficiency as well as the least nutrient loss. Adjusting fertilization rates can reduce soil and water contamination around the nursery without compromising growth performance, which reduces both producer’s investments and environmental impacts.

Nursery location and potassium enrichment in Aleppo pine stock 1. Effect on nursery culture, growth, allometry and seedling quality

This work was supported by the projects 'Improvement of reforestation in the province of Valencia through the definition of seedling quality standards' (20020995) and 'Establishment of protocols for seedling quality testing in nursery and field' (20080682), directed by the Polytechnic University of Valencia and the Valencian Regional Government (Generalitat Valenciana).