Deep-water Populations Research Articles

Seasonal patterns of carbohydrate translocation and synthesis of structural carbon components in Typha angustifolia

Quantitative studies of material budgets and resource allocation patterns of emergent plants are needed to fully understand nutrient and carbon cycling in wetlands. Whole-plant translocation patterns of nonstructural carbohydrates and synthesis of structural carbon were documented using two (shallow and deepwater) populations of Typha angustifolia in floodplain habitats of the Arakawa River, Japan. Monthly and bimonthly measurements of the concentrations of total carbon, non-structural carbohydrates, and water-soluble carbohydrates, as well as, estimates of standing stocks of aboveground (AG) and belowground (BG) biomass for both populations from 2002 to 2004 are described here. Annual patterns of carbon gain, rates of carbohydrate translocation between AG and BG organs, and rates of synthesis of structural carbon were estimated. Upward translocation supported all AG production for approximately 30 days. Afterward, the fraction of AG production supported by upward translocation decreased linearly with time, and completely diminished by Day 80 (counted from first day of growth; March 15). At Day 80, material translocation was directed downward and the percentage of downward translocation relative to AG net production increased until Day 170; there was a vigorous increase in downward translocation prior to senescence. In early summer (Day 80–110), more than half of the translocated materials were transformed into structural components, but by Day 125 only 30% was synthesized into total structural carbohydrates. Prior to senescence, there was a greater percentage of nonstructural carbohydrates in the rhizomes. Across the growing season (Day 60–153), the total amount of downward translocation was found to be proportional to AG production and the quantitative evaluation of the carbon budget shed further insight into the translocation process of this rhizomatous aquatic plants. In addition, insights on the differences between shallow and deepwater populations were gained. Especially, the deepwater population supported a higher fraction of vertical rhizomes compared to individuals sampled from the shallow water population.

Deep-water Ophiuroidea of the northern Atlantic with descriptions of three new species and taxonomic remarks on certain genera and species

Based on material from the fourth cruise of the RV Akademik Mstislav Keldysh and the MAR-ECO cruise of the RV G.O. Sars, 31 species of Ophiuroidea were identified from the section of the Mid-Atlantic Ridge between the Reykjanes Ridge and the Azores. The taxonomy of the group of genera with reduced arm comb and tentacle pores restricted only to the proximal arm segments is reviewed. It is suggested that the genera Homalophiura H.L. Clark, 1915, Ophiurolepis Matsumoto, 1915, Theodoria Fell, 1961 and Homophiura Paterson, 1985 should be regarded as synonyms of the genus Ophioplinthus Lyman, 1878. From examination of the type specimens, it is demonstrated that the six-armed species Ophiacantha anomala G.O. Sars, 1871 also includes five-armed specimens previously identified as the separate species Ophiacantha cuspidata Lyman, 1878. The latter taxon is considered here as the junior synonym of O. anomala. Previously mentioned ‘deep-water populations of the common shallow water species Ophiacantha bidentata (Retzius, 1805)’ represent a separate species, Ophiacantha fraterna Verrill, 1885, which is well distinguished by the shape of the spicules of the disk, narrow outer oral papilla and narrower tentacle scale as well as a hermaphroditic nature. Three new species, i.e. Ophioplinthus pseudotessellata sp. nov., Ophiocamax patersoni sp. nov. and Ophiophyllum nesisi sp. nov., are described.

Bacterioplankton communities of Crater Lake, OR: dynamic changes with euphotic zone food web structure and stable deep water populations

The distribution of bacterial and archaeal species in Crater Lake plankton varies dramatically over depth and with time, as assessed by hybridization of group-specific oligonucleotides to RNA extracted from lakewater. Nonmetric, multidimensional scaling (MDS) analysis of relative bacterial phylotype densities revealed complex relationships among assemblages sampled from depth profiles in July, August and September of 1997 through 1999. CL500-11 green nonsulfur bacteria (Phylum Chloroflexi) and marine Group I crenarchaeota are consistently dominant groups in the oxygenated deep waters at 300 and 500 m. Other phylotypes found in the deep waters are similar to surface and mid-depth populations and vary with time. Euphotic zone assemblages are dominated either by β-proteobacteria or CL120-10 verrucomicrobia, and ACK4 actinomycetes. MDS analyses of euphotic zone populations in relation to environmental variables and phytoplankton and zooplankton population structures reveal apparent links between Daphnia pulicaria zooplankton population densities and microbial community structure. These patterns may reflect food web interactions that link kokanee salmon population densities to community structure of the bacterioplankton, via fish predation on Daphnia with cascading consequences to Daphnia bacterivory and predation on bacterivorous protists. These results demonstrate a stable bottom-water microbial community. They also extend previous observations of food web-driven changes in euphotic zone bacterioplankton community structure to an oligotrophic setting.

Growth dynamics and biomass allocation of Eleocharis sphacelata at different water depths: observations, modeling, and applications

Imbalanced biomass allocation patterns in emergent aquatic plants to above and below-ground structures as a response to climatic variations and water depth were investigated on the basis of observation of three stable homogeneous populations established under different water regimes and climatic environments in Goulburn and Ourimbah, New South Wales, Australia, from August 2003 to December 2004. The growth of shoots depended on water inundation-drawdown patterns and climatic variations. Shoot density was greater in shallow water but with shorter shoot length and less maximum above-ground biomass density than for plant stands in deep water. Deep-water populations attained higher below-ground biomass with higher above to below-ground biomass ratio than for the shallow-water population. Translocation of carbohydrate reserves between above and below-ground organs in deep-water populations were mostly downward throughout the year whereas the depletion–recharge pattern varied seasonally in shallow water populations. Shoots of deep-water populations grew year-round whereas in shallow water shoots died off after recession of the water level with no re-growth afterward, showing that Eleocharis sphacelata is better adapted to deep water and is stressed under shallow-water conditions. A mathematical model was formulated to describe the growth patterns of E. sphacelata and subsequently to predict the effect of water depth on production. Model simulations are in satisfactory agreement with observed patterns of growth. The model also predicts that maximum production decreases sharply with increasing water depth.

Dynamics of carbon allocation in a deep-water population of the deciduous kelp Pleurophycus gardneri (Laminariales)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 309:143-157 (2006) - doi:10.3354/meps309143 Dynamics of carbon allocation in a deep-water population of the deciduous kelp Pleurophycus gardneri (Laminariales) Clare Margaret Dominik1,*, Richard C. Zimmerman1,2 1The California State University, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, California 95039, USA 2Present address: Department of Ocean, Earth and Atmospheric Sciences, 4600 Elkhorn Avenue, Old Dominion University, Norfolk, Virginia 23529, USA *Email: dominik@amarine.com ABSTRACT: Pleurophycus gardneri (Laminariales) is common in the low intertidal of the Northeast Pacific, but dominates many deep (30 to 40 m) rocky reefs in central California. Seasonal dynamics of productivity and resource allocation of a deep-water population of this deciduous, stipitate kelp were studied to understand how blade abscission affects the annual carbon budget. Patterns of growth, metabolism, and carbon storage and mobilization were measured monthly for 1 yr relative to in situ light and temperature, and used to model the annual carbon budget. The resulting carbon budget was used to determine if blade abscission effectively reduced respiratory demand during the winter period of low light availability. Metabolic properties (photosynthesis, photoacclimation, and respiration) were seasonally constant and showed evidence of photoacclimation to this deep, low-light environment. Blades grew between February and July, followed by senescence and sloughing from August to December. Concentrations of laminaran and mannitol decreased in the blades from the onset of sloughing in August until just prior to blade abscission in mid-December, suggesting translocation of these carbohydrates may have occurred from the blade to the stipe and holdfast. Carbon budget estimates revealed that scalar irradiance measures overestimated the light available for photosynthesis of these paddle-shaped kelp blades by 50 to 75%. The calculations also revealed that blade retention allowed for the maintenance of positive carbon balance throughout the year. Thus, conservation of the internal carbon reserve for metabolic survival during the low-light period does not appear to be a viable explanation for the deciduous life history of P. gardneri. Abscission may reduce hydrodynamic drag, thus minimizing the probability of dislodgment of entire plants during winter storm events, or promote spore dispersal as abscised blades and sori drift away from the parent holdfast. KEY WORDS: Carbon budget · Photosynthesis · Abscission · Light acclimation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 309. Online publication date: March 15, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Effects of water depth and litter accumulation on morpho-ecological adaptations of Eleocharis sphacelata

The morpho-ecological adaptations of Eleocharis sphacelata in response to water depth and the sequential effects of resultant differences in deep water conditions on the long term population dynamics were investigated based on the observations carried out in three stable homogeneous populations in Goulburn and Ourimbah, New South Wales, Australia from August 2003 to May 2005. The deep water populations attained a higher harvestable shoot biomass and a lower rhizome biomass with increased growth in root structure thus significantly enhancing the nutrient uptake rates leading to a higher accumulation of shoot bound macronutrients. However, the accretion of excessive amounts of autogenous shoot litter coupled with slower decomposition rates under anaerobic conditions in the two deep water populations led to higher nutrient enrichment in sediments and overlying water column causing subsequent eutrophication with signs of growth inhibition including typical stress symptoms like stunted growth and chlorotic shoots. The shallow water population that intermittently experienced alternative inundation-drawdown pattern depicted an unaffected continuation of seasonal growth affirming that strict water regime management practices coupled with timely mowing or the removal of accumulating litter are necessary to ensure long-term survival of healthy E. sphacelata stands when it is used in applications where deep water conditions prevail.

Life history flexibility allows Sargassum polyceratium to persist in different environments subjected to stochastic disturbance events

Stochastic, stage-based matrix models were used to investigate the life history strategy of the seaweed Sargassum polyceratium in shallow intertidal and deep-water (18 m) populations. Matrix models were parameterized with 3 years of yearly transitions among four plant stages quantified from three bays on Curacao (Netherlands Antilles). There were years without a storm, with a moderate (winter) storm and with a strong storm (Hurricane Lenny). The stochastic population growth rate varied among populations (λs: 0.54–1.03) but was not related to depth. The most important stages for population growth were reproductive adults (shallow) and non-reproductive adults (deep). With the occurrence of storms, vegetative growth (mainly deep) and fertility (mainly shallow) became the most important processes. Recruitment (shallow) and regeneration from holdfasts (deep) only contributed to population persistence after the hurricane. It is concluded that S. polyceratium has a flexible, depth-dependent, life history strategy that is adjusted to disturbance events.

Effects of wave exposure and depth on biomass, density and fertility of the fucoid seaweed Sargassum polyceratium (Phaeophyta, Sargassaceae)

Sargassum polyceratium is widely distributed around the island of Curaçao (Netherlands Antilles) where it inhabits strongly contrasting habitats. Changes in population structure have been followed in three bays with increasing levels of wave exposure at two depths: shallow (0 m) and deep (18 m). The effects of increasing wave exposure were investigated by studying three deep-water populations; and the effects of depth by studying shallow- and deep-water populations in the two calmer bays. Total density and stage density (reproductive thalli, juvenile thalli) were determined and total and individual thallus biomass was estimated non-destructively. In the most wave-exposed deep-water population thalli were twice as long with more than twice the biomass than in the calmest deep-water population. Total density and juvenile density were highest in the bay with intermediate wave exposure. Depth was an important factor at both the individual and population level. Shallow-water thalli had basal holdfast areas that were four times larger than those from deep water, and thallus biomass was positively correlated with holdfast area. Shallow-water juveniles invested more in the development of a holdfast and lateral growth than deep-water juveniles. Total biomass per quadrat was up to 10-fold higher in shallow- than in deep-water populations. In shallow-water populations reproductive thalli were present throughout the year whereas in deep-water populations they were present only during autumn and winter. We conclude that both wave exposure and depth affect population structure. Thalli were generally bigger and total biomass higher in the more exposed bay(s) and in shallower water, contradicting the general pattern in macroalgae of reduced size and biomass with increasing wave exposure.

Phenology of a deep-water population of Caulerpa racemosa var. cylindracea in the northwestern Mediterranean Sea

Phenology of a deep-water population of Caulerpa racemosa var. cylindracea in the northwestern Mediterranean Sea

Giant kelp (Macrocystis pyrifera) survival in deep water (25–40 m) during El Niño of 1997–1998 in Baja California, Mexico

During the 1997-1998 El Nino, we examined seasonally a giant kelp population in deep water (25-40 m) off the coast of Northern Baja California. Though most popula- tions in the region completely disappeared, large fertile adults survived the entire warming event at depth. At 25 m, there was no significant change in density or num- ber of fronds per individual during the warming period from spring 1997 to spring 1998, though the surface can- opy sloughed off (died) down to 15 m depth. By summer 1998, recruitment occurred at all depths at the site. Adult survival at depth was most likely important in post-dis- turbance recovery in surrounding populations by occu- pying substratum, providing vegetative growth, and producing spores. Survival in deep water during this extreme El Nino may have been due to local hydrogra- phy, such as internal waves bringing cool nitrate-rich water into the deeper regions of the shelf from below the thermocline, providing a refugium against the warm tem- peratures, low nutrients, and heavy wave action associ- ated with warming events. Deep-water populations may regularly survive El Nino warming in this region due to internal wave activity, and go undetected due to the depth at which they occur and the sloughing of the shal- low (-15 m) biomass.

Can ecological knowledge catch up with deep-water fishing? a North Atlantic perspective

Deep-water fishes have only recently moved from being objects of scientific curiosity to objects of commercial exploitation. For an increasing number of species, today a single trawl captures more specimens than science has ever seen since the time of Linnaeus. The deep-water environments now being fished are more complex both physically and biologically in general than is the shallower continental shelf, yet the shelf experience directs deep-water fishery expansion. Ecological considerations suggest that deep-water populations and ecosystems may be even more vulnerable to disruption than were those of the shelf. But the rate at which scientific study progresses lags well behind the rate at which deep-water fisheries develop. It often seems, in fact, that a fishery may be over before scientific study begins in earnest. Approaches to understanding based on theory and a holistic appreciation of how the deep-water world works can help, as can critical examination and mapping of a fishery’s history.

Photosynthetic utilisation of carbon and light by two tropical seagrass species as measured in situ

In situ measurements of seagrass photosynthesis in relation to inorganic carbon (Ci) availability, increased pH and an inhibitor of extracellular carbonic anhydrase were made using an underwater pulse amplitude modulated (PAM) fluorometer. By combining the instrument with a specially designed Perspex chamber, we were able to alter the water surrounding a leaf without removing it from the growing plant. Responses to Ci within the chamber showed that subtidal plants of the seagrasses Cymodocea serrulata and Halophila ovalis had photosynthetic rates that were limited by the ambient Ci concentration depending on the irradiance that was available during short-term photosynthesis–irradiance trials. Relative electron transport rates (RETRs) at light saturation (up to 500 μ mol photons m−2 s−1) increased by 66–100% when the Ci concentration was increased from ca. 2.2 to 6.2 mM. On the other hand, intertidal plants of the same species exhibited a much lesser limitation of photosynthesis by Ci at any irradiance (up to 1500 μ mol photons m−2 s−1). Both species were able to use HCO−3 efficiently, and there was stronger evidence for direct uptake of HCO−3 rather than extracellular dehydration of HCO−3 to CO2 prior to Ci uptake. Subtidally, H. ovalis and C. serrulata grew to 10 and 12 m, respectively, where ambient irradiances were approximately 16 and 11% of those at the surface. Maximum RETRs (at light saturation) were lower for these deep-growing plants than for the intertidally growing ones. For both species, the onset of light saturation of photosynthesis (Ek) occurred at approximately 100 μ mol photons m−2 s−1 for the deep water populations, which was four and two times lower than for the shallow populations of C. serrulata and H. ovalis, respectively. This, and the differences in maximal photosynthetic rates (RETRmax), reflects an acclimation of the deep-growing populations to the lower light environment. The results presented here show that photosynthesis, as measured in situ, was limited by the availability of Ci for the deeper growing plants in Zanzibar, while the intertidally growing plants photosynthesised at close to Ci saturation. The latter result is contrary to previous conclusions regarding Ci limitations for these intertidal plants, and, in general, our findings highlight the need for performing similar experiments in situ rather than under laboratory conditions.

Century-long effects of forest harvest on the physical structure and autotrophic community of a small temperate lake

The effects of forest clearcut and regrowth on a small (8.1 ha) stained lake were studied using a 200-year record of fossil carotenoids and chlorophylls. Comparison of high-resolution cores recovered from exposed, sheltered, and reference lake basins showed that annual laminations of sediments ceased concomitant with logging (ca. 1870-1890), indicating a fundamental change in the lake mixing regime. Biological responses to forest harvest included elimination of deepwater populations of anaerobic photosynthetic bacteria and reduced abundance of metalimnetic chrysophytes. Photosynthetic bacteria remained absent for over 100 years, while sediment laminae and chrysophytes have only returned since around 1970. In contrast, populations of epilimnetic phytoplankton (cyanobacteria, chlorophytes, cryptophytes) were unaffected by the clearcut. Analysis of sediment profiles did not reveal evidence of eutrophication or of increased flux of organic matter following watershed disturbance. Instead, fossil records were most consistent with increased wind stress, leading to deeper water column mixing in fall and reduction in deepwater anoxia, the main factor promoting sediment laminations and populations of photosynthetic bacteria. Such century-long disturbance may be common in small, stratified boreal lakes that lack physical shelter due to landforms.

Century-long effects of forest harvest on the physical structure and autotrophic community of a small temperate lake

The effects of forest clearcut and regrowth on a small (8.1 ha) stained lake were studied using a 200-year record of fossil carotenoids and chlorophylls. Comparison of high-resolution cores recovered from exposed, sheltered, and reference lake basins showed that annual laminations of sediments ceased concomitant with logging (ca. 1870-1890), indicating a fundamental change in the lake mixing regime. Biological responses to forest harvest included elimination of deepwater populations of anaerobic photosynthetic bacteria and reduced abundance of metalimnetic chrysophytes. Photosynthetic bacteria remained absent for over 100 years, while sediment laminae and chrysophytes have only returned since around 1970. In contrast, populations of epilimnetic phytoplankton (cyanobacteria, chlorophytes, cryptophytes) were unaffected by the clearcut. Analysis of sediment profiles did not reveal evidence of eutrophication or of increased flux of organic matter following watershed disturbance. Instead, fossil records were m...

Morphometric and meristic differences between shallow- and deep-water populations of white hake (Urophycis tenuis) in the southern Gulf of St. Lawrence

Linear discriminant function analysis of morphometric and meristic characters was used to assess the extent of differentiation between shallow- (<100 m) and deep- (>200 m) water populations of white hake (Urophycis tenuis) from the southern Gulf of St. Lawrence (NAFO Division 4T). Although meristic characters provided some evidence for stock separation, the best statistical separation was obtained with morphometric characters. Morphometric discriminant functions derived from "learning" samples were able to correctly classify 82 and 84% of the "test" samples for both females and males, respectively. A greater relative snout length in fish sampled from along the Laurentian Channel compared with those from the Northumberland Strait area was the primary discriminating character for both sexes. Our morphological evidence and previous tagging and distributional studies suggest that the populations from these two areas represent separate stocks; therefore, the traditional management unit for white hake in NAFO Division 4T may no longer be appropriate.

Molecular Genetic Analysis of Atlanto-Scandian Herring(Clupea Harengus)Populations Using Allozymes and Mitochondrial Dna Markers

Allozymes and restriction fragment length polymorphisms (RFLP's) in genes of the NADH dehydrogenase complex (ND 5/6 genes) of mitochondrial DNA (mtDNA) were used to investigate the spatial genetic structure of Atlanto-Scandian herring(Clupea harengus).Samples (sample size=46–50/site) comprised Icelandic summer spawners, Norwegian spring spawners, and two fjord populations, Balsfjord and Trondheimsfjord, on the Norwegian coast. Fifty enzymes were assayed, and samples were routinely examined at 18 enzymes comprising 28 putative allozyme loci. Significant genetic differentiation(P <0.001) was detected between Trondheimsfjord herring and all other samples, with apparent genetic homogeneity among remaining samples, including the Balsfjord; a region shown previously to contain an allozymically distinct population. Herring from the Balsfjord were shown allozymically to represent the Norwegian spring spawning group, suggesting the presence of two stocks, a deeper resident spawning (Balsfjord) and a shallower, non-native feeding population (Norwegian spring spawning). Variation at the ND5/6 genes using six restriction enzymes revealed 96 composite haplotypes in 196 fish. Mean haplotype diversity was high (0.92), though nucleotide divergence between samples was small (highest=0.00029, between Trondheimsfjord and Balsfjord samples; lowest=0.00003, between Icelandic summer and Balsfjord samples). Monte-Carlo %2analysis of haplotype frequencies revealed no significant geographic heterogeneity among samples, thus revealing a discordant pattern of genetic differentiation produced by allozymes and mtDNA markers. The detection of a genetically divergent population in deeper waters of the Trondheimsfjord supports the existence of distinct deep-water resident populations in the Norwegian fjords.

A genetic and morphological comparison of shallow- and deep-water populations of the introduced dreissenid bivalve <I>Dreissena bugensis</I>

A genetic and morphological comparison of shallow- and deep-water populations of the introduced dreissenid bivalve <I>Dreissena bugensis</I>

Morphometric and meristic differences between shallow- and deep-water populations of white hake (<I>Urophycis tenuis</I>) in the southern Gulf of St. Lawrence

Morphometric and meristic differences between shallow- and deep-water populations of white hake (<I>Urophycis tenuis</I>) in the southern Gulf of St. Lawrence

Sensitivity of intertidal and subtidal red algae to UVA and UVB radiation, as monitored by Chlorophyll fluorescence measurements: Influence of collection depth and season, and length of irradiation

Thirteen species from the red algal flora of Helgoland (southern North Sea) were exposed to UVA + UVB radiation for various periods in the laboratory, and dark-adapted variable fluorescence (F v:F m) was measured immediately after the UV treatment and again after various recovery times in white light. With the exception of Porphyra umbilicalis, all species showed a decrease in F v:F m on exposure to UV radiation, followed by recovery towards the initial values during the next 24–48 h in white light. The rate of the initial decrease was greater, and the extent of recovery was less, in deep subtidal species (e.g. Delesseria sanguinea, Plocamium cartilagineum) than in intertidal or shallow subtidal species, although there was no direct correlation between these indicators of sensitivity to UV radiation and the depth range of a species, and only slight differences were detected between populations of a single species collected from different depths. There was also little evidence of a seasonal change in sensitivity to UV radiation in Delesseria or Plocamium. The decrease in variable fluorescence in Delesseria and Plocamium was proportional to the logarithm of the exposure to UV radiation, and reciprocity between irradiance and the length of irradiation appeared to hold for up to 16h. The exposure to UVA that reduced F v:F m by 50% (‘50% exposure’) immediately after the treatment was about 10 kJ m-2 for both Delesseria and Plocamium, but Plocamium appeared to recover more rapidly than Delesseria because the 50% exposure after 24 h recovery was about 37 kJ m-2 for Delesseria compared with 70–120 kJ m-2 for different populations of Plocamium. The removal of UVB from the UV radiation treatments had no detectable effect on the inhibition of F v:F m in either Delesseria or a deep-water population of Plocamium, but reduced the inhibition by 30–50% in a shallow-water population of Plocamium. When only half an intact blade of Delesseria was exposed to UV radiation, variable fluorescence was reduced in the irradiated half but was completely unaffected in the unirradiated half, and steep gradients of F v:F m values were measured which persisted for over 48 h after the irradiation treatment.

Evidence of autumn nitrogen limitation and contribution of picoplankton to carbon fixation in Lake Tahoe

Water samples were collected from Lake Tahoe at midlake and nearshore stations at three depths (25, 50, and 75 m, corresponding to light intensities of approximately 10, 1, and 0.1% of surface light) in May and September. The water samples were evaluated to decide the following: (1) whether carbon fixation was N-limited and whether there were differences between picoplankton and larger phytoplankters and (2) the relative importance of picoplankton carbon fixation and related photosynthetic parameters. Evidence of N-limitation was observed only in September at the midlake station for the populations at 50 and 75 m, and to a lesser extent at the nearshore station at 75 m, but only for the nanoplankton fraction. The contribution of picoplankton to total carbon fixation ranged from 34 to 69% and did not increase with depth. Low values for Ik, the photoadaptation parameter, for deep water populations (0.1% light level) in September, but not May, suggested that these populations were adapted to low light in the fall but not the spring.