Verification of fractal growth models of the sponge Haliclona oculata (Porifera) with transplantation experiments

The growth form of the sponge Haliclona oculata is to a significant extent determined by the environmental conditions in which the form emerges. One of the main environmental parameters affecting the growth form is exposure to water movement. In this study, a morphological growth model is used to simulate the effect on the growth process of a change in exposure to water movement. Predictions based on the model are verified by experiments in which sponges from a sheltered growth site are transplanted to an exposed site, and vice versa. The effect of the transplantation on growth forms is determined by morphological comparisons. By combining the morphological simulation model with interpretation of growth forms, it becomes possible to use the growth form of H. oculata for bio-monitoring purposes. This form reflects the environmental conditions governing the growth process.     

Forest growth in the light of the thermodynamic theory of ecological systems

The observed growth of a particular forest stand can be described by many models and explained by some of them. The forest growth models are also successfully applied for extrapolating the growth curve. However, the known models of forest growth are not “one-point” models. They are not designed to predict the future growth of a forest stand from its current state: the model parameters either are not directly measurable or cannot be measured with relevant accuracy. This article is an attempt to use Jørgensen–Svirezhev theory as a new clue to the choice of variables that determines forest growth. The postulates of this theory combined with the pipe theory of tree growth lead to conclusion that biomass of a stand should be proportional to the four-fifths power of its age. Empirical validation, however, disclosed that calendar age is rather approximate measure of ecosystem ontogeny. Delayed development or intensive thinning of a forest stand at the early stages leads to rejuvenation bias. Thus derived 4/5-law model approximates well-known Chapman–Richards model in the neighborhood of the inflection point, and is applicable to middle-aged forest stands.     

Modelling growth forms of the spongeHaliclona oculata (Porifera,Demospongiae) using fractal techniques

The radiate-accretive growth process of the spongeHaliclona oculata, under different environmental conditions, is simulated in a two-dimensional model with fractal modelling techniques. In this model material is added in layers to the object, and growth velocities attain highest values at its protrusions. With this model some aspects of the growth process can be explained. It is possible to simulate thin-branching growth forms, which are normally found under sheltered conditions, and plate-like forms, which are typical for sites more exposed to water movement. These simulated forms are compared with actual growth forms in order to test the validity of the model.     

Growth and production of Euphausiacea (Crustacea) in the Rockall Trough

The euphausiid fauna of the Rockall Trough has been sampled in time series at approximately two-monthly intervals between 1973 and 1976 between surface and depths greater than 2000 m. Length/frequency histograms have modes that are coherent for periods of at least 4 to 6 mo, indicating that populations are being sampled. Rates of growth were determined for six species. Epipelagic species have winter checks to the growth rates, but such checks are absent in the growth of Thysanopoda acutifrons, Nematobranchion boöpis and Stylocheiron maximum. Ratios of annual production: biomass were determined and are all within the previously determined range of values for epipelagic and coastal populations. Lack of a winter check to the growth rate in deep-living species enables these potentially to have overall rates of growth comparable to those of temperate, epipelagic, shelf and coastal species.     

Age determination of the soft-shell clam Mya arenaria using shell internal growth lines

Shells of known-age Mya arenaria have revealed an internal annual growth pattern in this bivalve. The number of external growth rings on the shell exterior does not correspond to the age of the clams. This study provides an alternative method to using external annual rings for age determination. The internal growth lines are visible in thin sections when the shells are cut from the umbo to the ventral margin. The lines are formed by late spring of each year prior to spawning and are probably in response to decreased winter growth. When the 7 year olds were examined it was difficult to distinguish the most recent growth line and the inner shell layer. This could result in ages being underestimated. This annual pattern of internal growth lines could be useful to biologists and paleoecologists engaged in population studies.     

Rate of growth and longevity of a large colony of Pentapora foliacea (Bryozoa) recorded in their oxygen isotope profiles

We studied the growth patterns and the stable oxygen isotopic composition of an individual of Pentapora foliacea (Ellis and Solander 1786) collected on October 6, 1978 from the Bristol Channel, Pembrokeshire, UK, Irish Sea. The stable oxygen isotopes are in equilibrium with the ambient seawater and show a marked seasonal variation reflecting seasonal water temperature changes. The stable oxygen isotopes further suggest that regular growth patterns of less calcified growth bands, which are secreted in winter, are perennial. These winter growth check lines can easily be used to determine longevity of these bryozoa colonies and of annual growth rates. The colony analysed is at least 3-years-old with an annual growth rate of approximately 2 cm per year.     

The Potential for Species Conservation in Tropical Secondary Forests

Abstract: In the wake of widespread loss of old‐growth forests throughout the tropics, secondary forests will likely play a growing role in the conservation of forest biodiversity. We considered a complex hierarchy of factors that interact in space and time to determine the conservation potential of tropical secondary forests. Beyond the characteristics of local forest patches, spatial and temporal landscape dynamics influence the establishment, species composition, and persistence of secondary forests. Prospects for conservation of old‐growth species in secondary forests are maximized in regions where the ratio of secondary to old‐growth forest area is relatively low, older secondary forests have persisted, anthropogenic disturbance after abandonment is relatively low, seed‐dispersing fauna are present, and old‐growth forests are close to abandoned sites. The conservation value of a secondary forest is expected to increase over time, as species arriving from remaining old‐growth forest patches accumulate. Many studies are poorly replicated, which limits robust assessments of the number and abundance of old‐growth species present in secondary forests. Older secondary forests are not often studied and few long‐term studies are conducted in secondary forests. Available data indicate that both old‐growth and second‐growth forests are important to the persistence of forest species in tropical, human‐modified landscapes.     

Relationship between larval and juvenile growth rates in two marine gastropods,Crepidula plana and C. fornicata

Previous studies on various marine mollusc species have shown that both larval and juvenile growth rates are substantially heritable, but few workers have examined the extent to which larval and juvenile growth rates covary. We examined the relationship between larval and juvenile growth rates in seven laboratory experiments conducted between 1986 and 1993, using the prosobranch gastropods Crepidula plana Say and C. fornicata (L.). In most experiments larvae were reared individually, measured twice nondestructively to determine larval grwoth rate, allowed or stimulated (daily 5-h exposure to 20 mM excess K⁺ in seawater) to metamophose, and then measured at least twice after metamorphosis to determine juvenile growth rates. Generally, there was no significant (p >0.10) relationship between larval and juvenile growth rates, suggesting that in these two species selection can act independently on the two stages of development. A positive correlation (p=0.007) between larval and juvenile growth rates was observed for C. fornicata in one experiment, but only for offspring from females maturing the most rapidly in laboratory culture. Even for these larvae, however, variation in larval growth rate explained<2% of the variation in juvenile growth rate, so that larval and juvenile growth rates are at most only weakly associated in this species.     

Relation of RNA/DNA ratios to growth for the scallop Euvola (Pecten) ziczac in suspended culture

We examined the relation of RNA/DNA ratios to growth for three size groups of the tropical scallop Euvola ziczac maintained in suspended culture at 8, 21 and 34 m in depth in the Golfo de Cariaco, Venezuel. Various growth parameters indicated that production decreased with depth. This was more likely due to a decrease in seston quality with depth than to temperatures or seston abundance (which were similar at the various depths studied). The RNA/DNA ratio was correlated with the G-index of muscle growth for juveniles (r ²=0.55). A much weaker correlation was observed for the maturing scallops (r ²=0.18), probably because of the interaction between reproductive and somatic growth. In fully mature scallops, somatic growth was negligible and the RNA/DNA ratios appeared to be inversely related to the level of physiological stress of the scallops. Whereas RNA/DNA ratios are difficult to interpret for maturing E. ziczac, because an increased ratio can be due to either increased gonadal or somatic growth, they are useful in predicting growth in juveniles and physiological stress in fully mature scallops.     

Modelling Replicated Weed Growth Data using Spatially-varying Growth Curves

Weed growth in agricultural fields constitutes a major deterrent to the growth of crops, often resulting in low productivity and huge losses for the farmers. Therefore, proper understanding of patterns in weed growth is vital to agricultural research. Recent advances in Geographical Information Systems (GIS) now allow geocoding of agricultural data, which enable more sophisticated spatial analysis. Our current application concerns the development of statistical models for conducting spatial analysis of growth patterns in weeds. Our data comes from an experiment conducted in Waseca, Minnesota, that recorded growth of the weed Setariaspp. We capture the spatial variation in Setaria spp. growth using spatially-varying growth curves. An added challenge is that these designs are spatially replicated, with each plot being a lattice of sub-plots. Therefore, spatial variation may exist at different resolutions – a macro level variation between the plots and micro level variation between the sub-plots nested within each plot. We develop a Bayesian hierarchical framework for this setting. Flexible classes of models result which are fitted using simulation-based methods.     

Context-dependent effects of nestling growth trajectories on recruitment probability in the collared flycatcher

Nestling growth is known as an important determinant of fitness in altricial birds, but its evolutionary potential has been debated, and little is known about detailed patterns of current selection on growth. Relationships are often reported between nestling growth and attributes of nestlings and parents, but the interpretation of these depends on the advantages a given growth difference confers to the chicks. Increased growth may have positive, negative or context-dependent effects on offspring fitness, but these effects are largely unknown in natural populations. We measured growth trajectories of body mass in fostered broods of collared flycatchers (Ficedula albicollis) in 3 years of contrasting food conditions. We examined the growth of young and their recruitment probability to the breeding population in relation to year quality, hatching rank, sex, paternal age and paternal attractiveness. We also looked at the interactive effects of growth and intrinsic offspring attributes on recruitment probability. The predictors of nestling growth and those of recruitment did not agree. Moreover, the recruitment consequences of a given nestling growth rate were significantly influenced by nestling rank and paternal ornamentation. Differential recruitment effects of nestling growth in relation to parental traits and nestling attributes suggest that using growth as a generally applicable measure of nestling quality may not be justified. These findings also have implications for morphological evolution and the indicator value of sexual signals.     

Growth and pollution convergence: Theory and evidence

Stabilizing pollution levels in the long run is a pre-requisite for sustainable growth. We develop a neoclassical growth model with endogenous emission reduction predicting that, along optimal sustainable paths, pollution growth rates are (i) positively related to output growth (scale effect) and (ii) negatively related to emission levels (defensive effect). This dynamic law reduces to a convergence equation that is empirically tested for two major and regulated air pollutants – sulfur oxides and nitrogen oxides – with a panel of 25 European countries spanning the years 1980–2005. Traditional parametric models are rejected by the data. More flexible regression techniques confirm the existence of both the scale and the defensive effect, supporting the model predictions.     

Pigment composition and photosynthesis in Sargassum muticum

Detailed analyses of the seasonal changes in pigment composition of Sargassum muticum (Yendo) Fensholt growing at Bembridge on the Isle of Wight (UK) between April 1977 and June 1978 are presented. These show a large decrease in pigment content as growth proceeds. Laboratory experiments on the change in pigment content of winter-form plants are also reported. The high pigment contents of the winter-form plants and the dilution of pigments with growth are suggested to permit the rapid extension growth of this alga in the spring.     

Depth limits of Bermudan scleractinian corals: a submersible survey

Depth distribution, zonation pattern and growth morphology of 17 hermatypic and 4 ahermatypic coral species were investigated at eight different locations along the Bermuda platform with the research submersible GEO and by SCUBA diving in August–September 1983. Hermatypic coral growth occurs to a depth of 50 to 70 m, with a single Montastrea cavernosa growing at 78 m. Dominant forms in shallow-water coral communities are Diploria sp. and Porites astreoides, while M. cavernosa, Agaricia fragilis and Scolymia cubensis occur in deep-water associations below 60 m. Vertical visibilities (up to 178 m) and distribution of the photosynthetically active radiation revealed good light penetration values (1% level at about 100 m depth), which should favour hermatypic coral growth to a much greater depth than it actually occurs. Nor should the prevailing temperatures limit the depth of coral growth. Most deep-water hermatypes observed grow on remnants of Pleistocene reefs down to about 60 m. The vast areas of large massed rhodolith nodules below 50 to 60 m are unsuitable bottom for coral colonisation. Macroalgae growth seems to be the strongest factor controlling coral growth in deep water. Bermuda stony corals have a low growth form diversity. Various intraspecific morphs may occur at the same as well as at different depths, with a general trend towards flatter shapes with depth. Comparison with a similar study on Red Sea corals suggests that annual distribution of radiant energy on the most northern Atlantic reefs of Bermuda may be responsible for the occurrence of flat and cuplike growth forms in relatively shallow water, and for the shallower depth limits of hermatypic growth.     

Growth of the deep-sea irregular sea urchins Echinosigra phiale and Hemiaster expergitus in the Rockall Trough (N.E. Atlantic Ocean)

Growth in the deep-sea irregular sea urchins Echinosigra phiale (family Pourtalesiidae) and Hemiaster expergitus (family Hemiasteridae) was studied from deep-sea samples taken during the years 1973 to 1985 from two stations at 2900 and 2200 m depth in the Rockall Trough (N.E. Atlantic Ocean). Growth zones, similar to those described from sea urchins in shallow water, are present as a series of wide white bands separated by narrow, dark rings in the calcite stereom of the test plates after heating to 350°C. In shallow water, such growth zones seem to result from seasonally varying growth rates. In the supposedly constant conditions in the deep sea, a seasonal growth pattern is unexpected but may occur in response to recently discovered annual pulses in downward flux of detritus from the euphotic zone, providing a seasonally varying food supply for such deposit-feeding species living in the bottom sediment. On this assumption, growth curves were fitted to counts of growth zones (as representing age in years), in the larger lateral and ventral test plates of E. phiale and H. expergitus. The opportunity was also taken to fit growth curves derived from counts of growth zones in samples of the inshore spatangoids Spatangus purpureus and Echinocardium pennatifidum. Plots of counts against test length of Echinosigra phiale and H. expergitus, although scattered and not clearly asymptotic, indicate, growth to be slower than in the two inshore spatangoids, and than in the coastal species Echinocardium cordatum, for which there are good recent growth data, available.     

Analysis of annual fluctuations of C. nodosa in the Venice lagoon: Modeling approach

A simple simulation model was developed to describe the growth trends of Cymodocea nodosa (Ucria) Ascherson based on data sets from the Venice lagoon. The model reproduces the seasonal fluctuations in the above and belowground biomass and in shoot density. The modeling results are in good agreement with data on net production, growth rates and chemical–physical parameters of water. It was assumed that light and temperature are the most important factors controlling C. nodosa development, and that the growth was not limited by nutrient availability. The aim was to simulate biomass production as a function of external forcing variables (light, water temperature) and internal control (plant density). A series of simulation experiments were performed with the basic model showing that among the most important phenomena affecting C. nodosa growth are: (1) inhibition of production and recruitment of new shoots by high temperature and (2) light attenuation due to seasonal fluctuation.     

Growth maximization in early sardine larvae: a metabolic approach

Sardine larvae are forced to grow as fast as possible to reduce larval mortality. Thus, changes in biochemical composition during the first steps of sardine larval growth are intended to maximize larval growth rate efficiency and survival. Protein and RNA weight-specific growth rates were the highest and their corresponding doubling times the shortest among all the biomolecules, reflecting the importance of fast growth during early stages of larval development. The protein percentage increased and the carbohydrate and lipid percentages decreased during early growth until they reached, respectively, a percentage of 73.7, 3.1 and 18.0%. These percentages would represent the optimal proportion of biochemical components in sardine early larvae and they are the result of the trade-off between, in the short term, the protein proportion necessary to optimize larval movement and growth and, in the long term, the minimum lipid percentage necessary to guarantee energy reserves to fuel metamorphosis. RNA/DNA ratio increases during larval growth up to an asymptotic optimal value of ≈3.5 in postflexion larvae. Nutritional condition of sardine larvae was good and was influenced by the parental effect through the egg biochemical composition and by the growth trajectory determined by the actual environmental conditions.     

Population structure and growth of Donax trunculus (Bivalvia: Donacidae) in the western Mediterranean

A comparison of shell growth in Donax trunculus (collected between 1988 and 1990 of Cullera, Spain) has been carried out using an analysis of cohort progression in monthly length frequency distributions, hyaline surface shell growth rings and internal microgrowth bands. In the Mediterranean there are two periods of recruitment of D. trunculus, one in the summer (July to September) and the other in winter (December to February). Clams recruited to the population in winter display a clear cessation in shell growth during the following summer which may possibly be correlated with spawning, whereas individuals of the summer recruited cohort show no growth cessation the following summer and continue to deposit shell during this period. The normally opaque shell of D.trunculus reveals the presence of translucent hyaline growth rings when the shells are backlit by a strong light source, and these have been shown to be laid down in the shell during summer months. Formation of a hyaline ring is accompanied by a narrowing of the microgrowth patterns present in shell sections. Both the hyaline rings and the length frequency distributions have been used to determine the age and growth rate of D. trunculus.     

Croissance et structure de l'opercule calcifié du gastéropode polynésien Turbo setosus (Prosobranchia: Turbinidae): détermination de l'âge individuel

Turbo setosus Gmelin were collected in 1979 and 1982 in French Polynesia (Tuamotu). Ground cross-sections of calcified opercula revealed 3 distinct types of growth lines (A, B and C), the appearance and periodicity of which are described. Two months after fluorescent labelling with alizarin and fluorescein, permanent marks were easily visible in the operculum, enabling the 3 types of growth lines to be interpreted and a growth pattern distinguished: Type A growth lines, which are very translucent under transmitted light, are irregularly deposited after individual traumatisms and are termed stress lines; Type B lines exhibit a regular periodicity and correspond to a daily growth rhythm; Type C lines reflect a subdaily growth pattern. Vital staining enabled calcification of the operculum to be followed, and the speed of deposition has been estimated. The textural organization of the organic and mineral phases varies according to operculum area and depends on local speed of growth. In those areas of rapid growth (more than 20 m d^-1), deposits are cone-shaped and interlocked, and in those areas where growth is slower (less than 20 m d^-1), this type of organization disappears and is replaced by a regular organization without cone-shaped deposits. The number of daily growth lines, counted on 66 opercula, allowed us to accurately assess individual age and longevity in this species, which did not exceed 3 yr in our sample.