This study presents a 10-year population-genomic survey of the microcrustacean Daphnia pulex, revealing genome-wide patterns of selection. The genome sequences of over 800 isolates show that selection is pervasive across the genome, but the genome is in near steady state with respect to selection, with average selection coefficients near zero. These results suggest that interannual fluctuating selection is a major determinant of standing levels of variation in natural populations, challenging the conventional paradigm for interpreting patterns of nucleotide diversity and divergence. The study also highlights the importance of considering temporal variation in selection intensity when interpreting population-genomic data. The study found that most nucleotide sites experience fluctuating selection with mean selection coefficients near zero, with little covariance in selection strength across time intervals. The results suggest that selection is distributed across numerous small linkage islands of observable selection influencing levels of nucleotide diversity. These findings challenge the conventional interpretation of nucleotide diversity and divergence as measures of random genetic drift and intensities of selection. The study also found that the average selection coefficient for minor alleles is weakly positive, and that the temporal variance of selection is significant. The results suggest that selection coefficients are influenced by linkage disequilibrium with other sites, and that the overall pattern of selection is consistent with the concept of quasi-neutrality. The study also found that the temporal covariance of selection intensity is significant, with some negative and positive covariances observed. The study also found that the average selection coefficient for sites with different functional significance is small, and that the average selection coefficient for minor alleles is slightly stronger than for major alleles. The study also found that the average selection coefficient for sites with different MAFs is small, and that the average selection coefficient for sites with different MAFs is significantly different. The study also found that the average selection coefficient for sites with different MAFs is small, and that the average selection coefficient for sites with different MAFs is significantly different. The study also found that the average selection coefficient for sites with different MAFs is small, and that the average selection coefficient for sites with different MAFs is significantly different. The study also found that the average selection coefficient for sites with different MAFs is small, and that the average selection coefficient for sites with different MAFs is significantly different.This study presents a 10-year population-genomic survey of the microcrustacean Daphnia pulex, revealing genome-wide patterns of selection. The genome sequences of over 800 isolates show that selection is pervasive across the genome, but the genome is in near steady state with respect to selection, with average selection coefficients near zero. These results suggest that interannual fluctuating selection is a major determinant of standing levels of variation in natural populations, challenging the conventional paradigm for interpreting patterns of nucleotide diversity and divergence. The study also highlights the importance of considering temporal variation in selection intensity when interpreting population-genomic data. The study found that most nucleotide sites experience fluctuating selection with mean selection coefficients near zero, with little covariance in selection strength across time intervals. The results suggest that selection is distributed across numerous small linkage islands of observable selection influencing levels of nucleotide diversity. These findings challenge the conventional interpretation of nucleotide diversity and divergence as measures of random genetic drift and intensities of selection. The study also found that the average selection coefficient for minor alleles is weakly positive, and that the temporal variance of selection is significant. The results suggest that selection coefficients are influenced by linkage disequilibrium with other sites, and that the overall pattern of selection is consistent with the concept of quasi-neutrality. The study also found that the temporal covariance of selection intensity is significant, with some negative and positive covariances observed. The study also found that the average selection coefficient for sites with different functional significance is small, and that the average selection coefficient for minor alleles is slightly stronger than for major alleles. The study also found that the average selection coefficient for sites with different MAFs is small, and that the average selection coefficient for sites with different MAFs is significantly different. The study also found that the average selection coefficient for sites with different MAFs is small, and that the average selection coefficient for sites with different MAFs is significantly different. The study also found that the average selection coefficient for sites with different MAFs is small, and that the average selection coefficient for sites with different MAFs is significantly different. The study also found that the average selection coefficient for sites with different MAFs is small, and that the average selection coefficient for sites with different MAFs is significantly different.